i 


MEDICAL    *SCH©®L 


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in  2007  with  funding  from 

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http://www.archive.org/details/actionmusclesOOmackrich 


THE   ACTION    OF   MUSCLES 


THE    ACTION    OF 
MUSCLES 

INCLUDING    MUSCLE    REST    AND 
MUSCLE   RE-EDUCATION 


WILLIAM    COLIN  MACKENZIE 

M.D.,  F.R.C.S.,  F.R.S.  (Edin.) 

/  Member  of  the  Council  of  the  Anatomical  Society  of  Great  Britain 

and  Ireland}  and  formerly  of  the  Staff  of  the  Military  Orthopaedic 

Hospital,  Shepherd's  Bush,  London  ;  formerly  Lecturer  on  Applied 

Anatomy  to  the  University  of  Melbourne,  and  Examiner  in  Senior 

Anatomy  to  the  Universities  of  Melbourne  and  Adelaide 


EDITED  BY 

CHARLES  MACKAY,  M.D. 
Major  R.A.M.C. 


WITH  09  ILL  USTRA  TIONS 


PAUL  B.  HOEBER 

67  &  69  EAST  59TH  STREET 

NEW  YORK 

1921 


Printed  in  England 


QP303 

M  IS 

19X1 


INTRODUCTION 

In  Army  medical  circles  the  view  is  held  that  of  the  wounded 
men  who  have  returned  from  the  French  battlefields  during 
the  Great  War,  some  65  per  cent,  are  suffering  from  dis- 
abilities of  an  orthopaedic  nature  ;  in  other  words,  whether 
the  injury  be  one  of  muscle,  bone,  joint,  nerve,  or  central 
nervous  system,  it  is  of  such  a  character  that  the  question 
of  muscular  function  becomes  of  prime  importance  for 
purposes  of  treatment.  When  we  consider  that  muscular 
tissue  alone  constitutes  the  largest  part  of  most  animals, 
it  is  surely  time  that  more  attention  was  paid  to  the 
teaching  of  myology  than  has  been  allowed  heretofore. 
Function  of  muscle — the  all-important  factor — cannot  be 
satisfactorily  taught  in  the  dissecting  room.  It  can  only 
be  taught  on  the  living,  and  is  largely  a  question  of  com- 
parison— a  comparison  between  the  normal  and  the  paralytic. 
Only  on  this  plan  can  the  question  of  origin  and  insertion 
of  a  muscle  have  more  than  an  academic,  or  rather  ex- 
amination interest  for  the  student. 

Just  as  important  as  a  knowledge  of  the  action  of  a 
muscle  is  a  knowledge  of  the  action  of  its  opponent,  and 
the  opponent  should  be  specifically  mentioned.  The  state- 
ment that  fifteen  external  rotators  of  the  hip,  including 
such  powerful  engines  as  the  psoas  and  great  gluteus,  are 
balanced  by  one  muscle  and  part  of  another,  can  no  longer 
be  tolerated.  The  fact  that  the  student  when  learning  the 
action  of  a  muscle  learns  that  of  the  opponent  will  have 
an  important  influence  on  his  treatment,  for  example,  of 
muscular  weakness,  or  paralysis,  or  of  joint  injuries.  Thus 
in  a  case  of  weakness  of  the  deltoid  he  will  associate  with 
that  muscle  the  opposing  adductor,  namely,  the  pectoralis 


1016 


Ml 


vi  INTRODUCTION 

major.  He  will  recognize  that  there  can  be  no  recovery 
if  the  opposing  pectoral  be  allowed  to  contract,  and  will 
immediately  guard  against  this  occurrence. 

As  the  muscles  of  the  human  body  are  adaptive  or 
survival  results  of  struggles  which  have  gone  on  during 
the  past  ages,  it  follows  that  some  appreciation  of  their 
comparative  anatomy  is  essential  for  the  clinician.  It  is 
inconceivable  that  any  one  should  attempt  to  handle  a 
paralysed  deltoid  or  quadriceps  without  some  knowledge  of 
its  ancestral  history,  or  of  the  entities  of  which  its  function 
is  composed. 

Muscle  fibre  is  delicate,  sensitive,  and  responsive.  It 
can  be  coaxed  but  not  driven.  It  should  be  conserved  and 
not  indiscriminately  torn  or  cut  through  at  surgical  opera- 
tions as  though  of  no  account.  In  any  "  orthopaedic  " 
condition  the  muscle  should  be  looked  on  as  a  friend,  ready 
to  do  our  bidding  if  placed  under  proper  control.  It  should 
not  be  asked  to  do  80  units  of  work  when  it  is  capable 
of  performing  only  40  units.  When  we  read  in  the  works 
of  H.  O.  Thomas  such  an  expression  as  "  which  the  muscles 
appear  to  know,"  we  instinctively  feel  that  when  Thomas 
treated  diseases  of  the  hip  the  muscular  sentinels  of  the 
joint  were  all  personalities  to  him.  In  this  way  also  were 
muscles  regarded  by  John  Hunter,  Charles  Bell,  Haller, 
and  Cowper,  who  all  devoted  a  large  part  of  their  scientific 
life  to  the  study  of  motion.  It  seems  extraordinary  that 
learned  discourses  should  be  devoted  to  a  nerve  case,  and 
that  the  muscles,  through  loss  of  whose  function  the  disease 
has  perhaps  been  recognized,  are  so  often  considered  as 
unworthy  of  even  physiological  rest. 

The  term  "  paralysis  of  muscle  "  is  at  present  much  too 
loosely  applied.  It  would  be  better  to  state  that  such  a 
condition  is  extremely  rare.  A  loss  of  part  of  the  function 
of  a  muscle  is,  on  the  other  hand,  common.  There  is 
only  one  true  test  of  muscle  function,  the  volitional  test 
scientifically  applied.  Any  other  test,  whether  from  the 
clinical  or  experimental  point  of  view,  is  unworthy  of 
consideration.    The  volitional  test  takes  into  consideration 


INTRODUCTION  vii 

not  only  the  affected  muscle,  but  its  reciprocal  elongator. 
It  is  the  only  test  by  which  the  muscle  can  be  considered 
from  the  point  of  view  both  of  comparative  anatomy  and 
of  mechanics,  as  is  shown  in  the  case  of  the  deltoid  and 
the  brachialis. 

Usually,  the  operator  when  he  has  surgically  finished 
with  a  case  in  which  muscle  function  is  involved,  passes  it 
on  for  massage  or  electrical  treatment,  both  of  which 
forms  of  treatment  are  purely  passive.  What  significance 
the  expression  massage  and  electricity  has  in  the  surgeon's 
mind  the  writer  has  often  longed  to  know.  In  poliomyelitis 
no  massage  or  electricity  should  be  applied  till  recovery  has 
taken  place.  These  forms  of  treatment  cannot  initiate 
muscle  function,  but  they  can  strengthen  the  action  of 
recovered  muscles.  The  principle  cannot  be  repeated  too 
often  that  an  ounce  of  scientifically  directed  volitional  effort 
is  worth  pounds  of  passive  treatment.  With  this  in  mind 
it  is  wonderful  what  can  be  accomplished  in  a  warm  room 
with  the  aid  of  a  table,  a  few  pillows,  and  a  sheet  of  pow- 
dered cardboard.  Such  indeed  might  be  termed  the  Depart- 
ment of  Myology.  To  this  simple  department  the  more 
complex  ones  of  massage,  electricity,  and  of  those  movements 
which  owe  their  name  sometimes  to  the  country  of  origin 
and  sometimes  to  their  inventor,  should  be  subsidiary. 
The  myologist,  looking  at  the  case  solely  from  the  point  of 
view  of  function,  should  determine  whether  in  traumatic 
cases,  at  what  stage,  and  of  what  nature,  massage  or  elec- 
trical treatment  or  both  would  be  beneficial.  These  should 
not  be  ordered  indiscriminately  and  as  a  matter  of  routine. 
To  many  this  may  seem  premature,  but  nevertheless  it  is 
only  a  question  of  time  when  a  Department  of  Myology  will 
be  a  principal  feature  in  every  Orthopaedic  Institution. 

The  writer  wishes  to  thank  the  President  and  Council 
of  the  Royal  College  of  Surgeons  of  England  and  also 
Professor  Arthur  Keith  for  the  privilege  of  having  been 
able  to  conduct  researches  at  the  Hunterian  Museum  during 
the  past  three  years  ;  Sir  Robert  Jones,  Inspector-General 
of   Military    Orthopaedics,    for   facilities   accorded   him   in 


viii  INTRODUCTION 

carrying  out  investigations  on  muscular  action  at  the 
Military  Orthopaedic  Hospital,  Shepherd's  Bush,  and  for 
his  permission  to  utilize  photographic  and  other  material ; 
the  Staff  of  the  Hospital  for  their  kindness  and  co-operation, 
especially  in  allowing  him  to  see  selected  cases  ;  and  Mr. 
Bird,  artist  to  the  Hospital,  for  the  trouble  taken  with  the 
photographs  ;  Mr.  Victor  Cobb,  of  Melbourne,  and  Mr.  Fin- 
nerty  for  their  excellent  drawings  ;  and  his  secretary,  Miss 
Olive  Hine,  for  help  in  the  preparation  of  the  manuscript. 

In  conclusion,  the  author  desires  especially  to  thank  his 
cousin,  Major  Charles  MacKay,  R.A.M.C,  for  his  generous 
assistance  extending  over  five  years  in  the  preparation  of 
numerous  specimens  and  dissections ;  also  for  his  constant 
help  and  advice  during  the  past  twelve  months. 

While  the  author  has  been  unavoidably  absent  in 
Australia,  Major  MacKay  has  kindly  undertaken  the  editing 
and  correcting  of  the  proof-sheets. 


PUBLISHERS'    NOTE 

The  gratifying  reception  accorded  to  Dr.  Mackenzie's  work 
having  made  a  reprint  necessary,  the  opportunity  has  been 
taken  of  correcting  some  printer's  errors,  while  the  Editor 
has  also  made  some  slight  alterations  and  additions.  A 
new  drawing  has  been  supplied  for  Fig.  85,  and  the  adop- 
tion of  a  smoother  surface  paper  will  be  found  to  have 
improved  some  of  the  illustrations  in  the  text,  which  were 
not  quite  satisfactory  in  the  first  impression. 


CONTENTS 


INTRODUCTION 


PAGE 

V 


CHAPTER    I 

PRINCIPLES       ..'... 
I.  Nature  of  Muscle 
II.  Muscle  Tendon 

III.  Relation  of  Bone  to  Muscle 

IV.  Origin  and  Insertion  of  Muscle 
V.  Ligaments 

VI.  Pulleys,  Sesamoids,  and  Levers 

VII.  Form  and  Arrangement  of  Muscle 

VIII.  The  Evolution  of  Muscular  Action  :  Muscle 

Re-education  . 

IX.  Muscle  Rest  :    Zero  Position 

X.   Chronic     Muscle     Shortening:      Contracted 

Muscles  .... 
XI.  Testing  for  Muscle  Action 

XII.  Correlations.     Muscle  Development  and  the 

Thymus  Gland 

XIII.  Contraction,  Relaxation,  and  Elongation  of 

Muscle  :    Elasticity 

XIV.  Reverse  Action 
XV.  Muscles  passing  over  Several  Joints 

XVI.  Specialization  of  Muscle  Function 
XVII.  Synergists.  .... 

XVIII.  Mechanism  of  Muscular  Contraction 


2 

4 
5 

7 
8 

12 


14 
18 


22 
28 

30 

36 
4i 
43 
44 
45 
46 


CHAPTER    II 


THE    SHOULDER    REGION 


48 


x  CONTENTS 

CHAPTER    III 

PAGE 

THE     BICEPS     BRACHII     AND     BRACH1ALIS  :       MUSCULO- 
CUTANEOUS  PARALYSIS 71 

CHAPTER    IV 
MEDIAN   NERVE   PARALYSIS 85 

CHAPTER    V 
ULNAR  PARALYSIS 97 

CHAPTER    VI 
MUSCULO-SPIRAL   PARALYSIS Ill 

CHAPTER    VII 
THE  MUSCLES   OF  THE   THIGH     .  .  .  .  .       127 

CHAPTER    VIII 
MUSCLES   ACTING   ON   THE   LEG  ....       145 

CHAPTER    IX 

MUSCLES      ACTING      ON      THE      FOOT      (GREAT      SCIATIC 

NERVE) •  .  .       168 

CHAPTER    X 
THE   MUSCLES  OF  THE  TOES    (GREAT   SCIATIC  NERVE)    .       182 

CHAPTER    XI 
MUSCLES   OF  THE   SPINE 200 


CONTENTS  xi 

CHAPTER    XII 


PAGE 


MUSCLES  WHICH   MOVE  THE   NECK      ....       206 
CHAPTER    XIII 

muscles     which     move     the     back     and     loins 

(thoracic  and  lumbar  regions)      .         .         .     213 

CHAPTER    XIV 
ANATOMICAL   CONSIDERATIONS   IN  JOINT  FIXATION        .       222 

CHAPTER    XV 
THE   MUSCLES   OF   RESPIRATION  ....       228 

INDEX 251 


LIST  OF  ILLUSTRATIONS 

PIG.  PAGE 

1.  TENDON  OF  ORIGIN  OF  MUSCLE  (MACERATED  SPECIMEN)  2 

2.  EXAMPLE    OF   LEVER   OF   FIRST   ORDER  ...  10 

3.  EXAMPLE    OF   LEVER   OF   SECOND    ORDER     .  .             .II 

4.  EXAMPLE    OF   LEVER   OF   THIRD    ORDER        ...  12 

5.  THE   LEG   AND   FOOT   OF   KANGAROO  ....         32 

6.  the  leg  and  foot  of  koala  (Phascolarctos  cinereus)       33 

7.  DIAGRAMMATIC  REPRESENTATION  OF  MUSCULAR  ACTION, 

AND   RECIPROCAL  ELONGATION  ...         37 

8.  QUADRICEPS         EXTENSOR        PARALYSIS        (INFANTILE 

PARALYSIS) 49 

9.  THE   DELTOID   REGION    OF   KOALA  50 

10.  MUSCLES  OF  THE    FORE  LIMB  OF  THE  WOMBAT  (PhasCO- 

lomys  Mitchelli)  ....         facing      50 

11.  THE  INSERTIONS  OF  MUSCLES  MOVING  THE  HUMERUS   .         53 

12.  BI-LATERAL    SERRATUS     PARALYSIS     OF    SIX    MONTHS' 

standing facing      58 

13.  COMPLETE  ELEVATION  OF  UPPER  LIMBS  WHEN  SITTING 

ERECT  AFTER  TEN  WEEKS'  REST  AND  RE-EDUCATION 

facing      58 

14.  POSITION    FOR   ANATOMICAL  REST.      FRONT  VIEW     „  58 

15.  POSITION    FOR   ANATOMICAL  REST.      BACK   VIEW        „  58 

16.  THE   INABILITY  WHEN  ERECT  TO  ELEVATE  THE   UPPER 

LIMBS   BEYOND   THE   RIGHT  ANGLE  .  facing        58 

17.  METHOD    OF   RE-EDUCATION        ...  58 

18.  THE   UPPER   LIMB   ABDUCTION    SPLINT 

19.  METHOD    OF   EDUCATION    FOR   SHOULDER   REGION 

20.  METHOD   OF   EDUCATION    FOR   SHOULDER   REGION 

21.  METHOD    OF   RE-EDUCATING   THE   DELTOID 

22.  ILLUSTRATING  METHOD  OF  EDUCATING  THE  DELTOID 

23.  STIFF     SHOULDER.        THE     PATIENT     WHEN     ERECT     IS 

UNABLE    TO    ABDUCT    THE    ARM    45    DEGREES    FROM 

THE   SIDE 

xiii 


59 
61 
61 

63 

64 


68 


xiv  LIST    OF    ILLUSTRATIONS 

FIG.  PAGE 

24.  WHEN     LYING     FLAT     ON     A     FIRM     TABLE     THE     SAME 

PATIENT   ABDUCTS   THE   ARM    READILY   TO   A   RIGHT 

angle facing      68 

25.  WHEN  LYING  FLAT  THE  SAME  PATIENT  CAN  PARTLY 

ELEVATE  THE  LEFT  UPPER  LIMB  ABOVE  THE  HEAD, 
i.e.   CAN  ENTER  THE  SECOND  OR  SCAPULA  ROTATION 

arc  .......  facing      68 

26.  ILLUSTRATING  "  REVERSE  ACTION  "   BY  THE  BRACHIA- 

LS  MUSCLE  .  .  .  .  .  .  -72 

27.  DISSECTION  TO  SHOW  FRONT  OF  FOREARM  AND  HAND. 

KANGAROO 74 

28.  BICEPS  BRACHII  AND    BRACHIALIS.      BICEPS    IN  PRONA- 

TION  AND    SUPINATION    OF   FOREARM       ...         76 

29.  NATURE'S   EXPERIMENTS  WITH   THE   BICEPS   BRACHII  .         78 

30.  POSITION  OF  REST  IN  MUSCULOCUTANEOUS  PARALYSIS 

facing       80 

31.  METHOD   OF  REST  IN   MUSCULOCUTANEOUS  PARALYSIS 

facing      80 

32.  COMMENCING     RE-EDUCATION      OF     THE     BRACHIALIS. 

NOTE   THE   SLIGHT   PRONATION    OF  THE   HAND  .  8l 

^.      BICEPS   AND    BRACHIALIS 82 

34.  BICEPS   AND   BRACHIALIS 82 

35.  BICEPS  AND  BRACHIALIS.      WORK  FOR  THE  BRACHIALIS 

is  increased facing      82 

36.  COMMENCING  RE-EDUCATION  FOR  THE  BICEPS  BRACHII 

facing      82 

^J.  RECOVERY   OF   BICEPS   SUPINATION  8^ 

38.  RECOVERY   OF   BICEPS   SUPINATION  8^ 

39.  THE   MOTOR   FORCES   WHICH   MOVE   THE   THUMB  .  .         86 

40.  RECIPROCAL     LEVERAGE     BY     THE     PROFUNDUS  AND 

SUBLIMIS  TO  IMPROVE  FLEXION  POWER  ...         88 

41.  POSITION    OF   REST   IN   MEDIAN   NERVE   PARALYSIS         .         91 
42.      METHOD     OF     EFFECTING     REST     IN     MEDIAN     NERVE 

paralysis  .....  facing      93 

43.  COMMENCING  RE-EDUCATION  OF  PRONATION.      MEDIAN 

NERVE   PARALYSIS  ....  facing  93 

44.  RE-EDUCATION    IN    MEDIAN   NERVE   PARALYSIS    .  .  94 

45.  RE-EDUCATION    IN    MEDIAN    NERVE    PARALYSIS     .  .  94 

46.  METHOD   OF  RESTING    (a)   AND   OF  RE-EDUCATING  THE 

THUMB    (b)    IN    MEDIAN    NERVE    PARALYSIS         facing         95 

47.  RE-EDUCATING   FINGER   FLEXION         .  .  .       ,,  95 


LIST    OF    ILLUSTRATIONS  xv 

FIG.  PAGE 

48.  HOW  FLEXOR  LEVERAGE  OF  THE  FINGERS  IS  IMPROVED 

BY  EXTENDING   (DORSI-FLEXING)   THE  WRIST  .  .  96 

49.  POSITION     OF    REST    FOR    THE    UPPER    EXTREMITY    IN 

ULNAR   PARALYSIS 102 

50.  RE-EDUCATION    IN    ULNAR   PARALYSIS  .  .  .  IO4 

51.  PARTIAL   ULNAR   PARALYSIS IO5 

52.  TESTING   AND   COMMENCING   RE-EDUCATION    IN   WEAK- 

NESS  OF  THE   EXTENSORS   OF  THE   FINGERS    (iNTER- 
OSSEI   AND    EXTENSOR   COMMUNIS)  .  .  .       IO7 

53.  INCREASING   THE   WORK   OF   THE    EXTENSORS    OF   THE 

FINGERS 108 

54.  PARTIAL   ULNAR   PARALYSIS IO9 

55.  MUSCULO-SPIRAL   PARALYSIS    (CHARLES   BELL)      .  .  II3 

56.  THE  ARRANGEMENT  OF  MOTOR  FORCES  ON  THE  DORSUM 

OF   THE    FINGER 115 

57.  POSITION    FOR    IMMEDIATE    REST    IN    MUSCULO-SPIRAL 

paralysis  .....  facing    117 

58.  RESTING    THE    HAND    IN     PARALYSIS    OF    THE    WRIST 

EXTENDERS    (THOMAS)  .  .  .  .  Il8 

59.  RE-EDUCATION   IN   MUSCULO-SPIRAL  PARALYSIS  .  .  120 

60.  MUSCULO-SPIRAL   PARALYSIS       .  .  .  facing  121 

61.  RE-EDUCATION    OF  THE   TRICEPS  ....  122 

62.  RE-EDUCATION    OF   THE  TRICEPS  ....  123 

63.  THE   RIGHT   LOWER   LIMB   SUPPORTING  THE  TRUNK  IN 

THE    ERECT    POSITION    OWING    TO    CONTRACTION    OF 

THE   GLUTEUS   MAXIMUS   AND   THE   QUADRICEPS         .       128 

64.  FLEXION     AND    EXTENSION    OF    THE    TRUNK    ON    THE 

THIGH 129 

65.  THE  DORSAL  ABDOMINAL  WALL  OF  THE  KANGAROO 

facing    131 

66.  THE   ERECT   POSTURE   OF  THE   KANGAROO  .  .  .       I32 

67.  TESTING   FOR   PSOAS   IRRITATION  ....       I33 

68.  DORSAL  DISSECTION   OF  PLATYPUS  TO   SHOW  GLUTEUS 

MAXIMUS   AND    BICEPS   CRURIS         ....       135 

69.  DISSECTION    TO    SHOW    BUTTOCK,    OUTER    THIGH,    AND 

LEG.      KANGAROO 137 

70.  THE   ADDUCTORS    OF   THE   THIGH  ....  I38 

71.  A  SIMPLE  ABDUCTION  OR  ADDUCTION  FRAME  .  .  I4O 
JZ.  THE  MUSCLES  WHICH  ROTATE  THE  FEMUR  .  .  I43 
y^'      DIAGRAM     ILLUSTRATING     THE     ACTION     OF     MUSCLES 

ACTING   ON    THE   LEG   AND   THIGH  .  facing      151 


xvi  LIST    OF    ILLUSTRATIONS 

FIG.  PAGE 

74-      DISSECTION  OF  INNER  SIDE  OF  KNEE.      WOMBAT  (PhdS- 

colomys  Mitchelli)       ......  152 

75.  MUSCLES  ON  VENTRAL  SURFACE  OF  THIGH.      PLATYPUS  153 

76.  INSERTION  OF  THE  QUADRICEPS  EXTENSOR  .  .  156 
yj.      COMPLETE   RECOVERY   OF   QUADRICEPS   ACTION    (MAXI- 
MUM work),    an  erroneous  method  of  testing 

FOR   PARALYSIS 1 63 

j8.      COMMENCING   RE-EDUCATION    OF   THE   QUADRICEPS        .  1 64 

79.  COMPLETE  RECOVERY  OF  QUADRICEPS.      IOO  UNITS  OF 

WORK,   OR   MAXIMUM 1 65 

80.  ALMOST  COMPLETE   RECOVERY   OF    QUADRICEPS    (SAME 

PATIENT  AS  FIG.   8l) l66 

81.  contracted  knee  of  ten  years'  duration,  the 

result  of  contraction  of  flexors  owing  to 

paralysed  quadriceps  (same  case  as  fig.  80)   .  l66 

82.  the  benders  (dorsi-flexors)  of  the  foot  .         .  1 69 
8^.    the  extenders  (plantar-flexors)  of  the  foot  .  1 72 

84.  extension  backwards  of  the  rigid  body  at  the 

ankle  joint      .......  175 

85.  acquired  deformities  of  the  foot     .         .         -179 

86.  the  muscles  of  the  big  toe  (hallux)  .         .         .  183 
8y.    inversion  of  the  foot  in  the  extended  position 

(tibialis  posticus) 194 

88.  a  useful  form  of  foot  splint.    the  arc  shoe   .  1 98 

89.  the  extenders  (dorsi  flexors)  of  the  head.    the 

ERECTOR   SPIN^E  AND   ITS   DIVISIONS        .  facing  202 

90.  THE   BENDERS    (WITH    GRAVITY)     OF    THE    HEAD    AND 

SPINE 210 

91.  FLEXION  OF  THE  RIGID  BODY  AT  THE  KNEE  JOINT      .  2l6 

92.  PELVIC   TILTING   FOLLOWING   POLIOMYELITIS         .  .  221 

93.  THE   EXTENDED   ARC   SPLINT 224 

94.  EFFECTIVE   SPLINT   FOR   RESTING  THE   KNEE   JOINT      .  225 

95.  DISSECTION   OF   VENTRAL  SURFACE   OF  THE   PLATYPUS 

(abdomen  and  thigh)         .         .         .         facing  230 

96.  INGUINAL  REGION    (MALE   PLATYPUS)  .  .  .  242 

97.  DISSECTION   TO   SHOW   PATENT   INTERNAL    ABDOMINAL 

RING    AND    CANAL    CONTINUOUS    WITH    THE    TUNICA 

VAGINALIS    (MALE   WOMBAT)  ....  243 

98.  DISSECTION    TO    SHOW    INGUINAL   REGION    (MALE   TAS- 

manian  VEVijJ^&asyums  sarcophilus)  facing  244 

99.  INGUINAL ^£GI0N    (MALE   WOMBAT)  ....  245 


THE  ACTION  OF  MUSCLES 


CHAPTER    I 
PRINCIPLES 

I.    Nature  of  Muscle 

The  skeletal  muscles  in  the  human  body  number  not  less 
than  434  and  constitute  the  largest  part  of  most  mammals, 
being~about  45%  of  the  total  weight.  Each  is  a  distinct 
organ  ;  each  a  simple  independent  force,  endowed,  since  it 
can  contract  and  shorten,  or  relax,  with  the  power  of  pro- 
ducing motion.  This  power  the  muscle  cell  shares  with  no 
other  in  the  body.  Each  muscle  cell  has  an  arterial,  venous, 
lymphatic,  and  nervous  supply — the  whole  constituting 
the  motor  engine.  By  means  of  the  nerves  extending 
between  the  central  nervous  system  and  the  muscles,  the 
force  of  contraction  inherent  in  each  muscle  cell  is  so 
directed  and  regulated,  as  to  be  of  greatest  service  in  the 
production  of  movement  in  the  body.  Through  the  nerves 
also,  the  combination  of  action  of  separate  muscles  so  as 
to  improve  power  is  effected,  as  for  example  in  external 
rotation  at  the  hip. 

Muscular  is  different  from  elastic  power,  since  for 
the  production  of  action  in  an  elastic  body  some  outside 
force  is  necessary.  Each  muscle  is  primarily  composed 
of  cylindrical  fibres  measuring  about  i-J-  inches  long  and 
1/500  inch  in  diameter,  and  each  fibre  or  cell  has  an  elastic 
sheath  or  wall — the  sarcolemma.  These  cylindrical  fibres 
I 


2  THE    ACTION    OF    MUSCLES 

are  held  together  by  connective  tissue  which  is  connected 
to  the  sarcolemma,  and  are  collected  into  bundles.  These 
bundles  or  fasciculi  are  also  held  together  by  connective 
tissue,  and  collectively  form  the  fleshy  mass  or  muscle. 
The  muscle  is  enclosed  in  a  membranous  sheath  which  is 
related  to  connective  tissue  binding  the  bundles.  Thus 
forming  the  organ  called  "  muscle  "  we  have  not  only  the 
special  cells  endowed  with  the  power  of  producing  motion, 
but  also  connective  tissue  elements  endowed  like  the  tendon 
not  with  the  power  of  producing  motion,  but  with  that  of 
elasticity  or  accommodation.  This  is  well  known,  but  its 
significance  clinically  does  not  appear  to  be  appreciated. 
It  has  an  important  bearing  on  the  question  of  so  called 
muscle  "  tone  "  and  "  contracted  "  muscle. 

II.    Muscle  Tendon 

Usually  we  find  that  at  its  origin  or  fixed  point,  and  at 
its  insertion  where  motion  takes  place,  the  muscle  belly  is 
attached  by  means  of  fibrous  tissue  known  as  tendon.     Just 


Fig.   i. — Tendon  of  origin  of  muscle  (macerated  specimen). 

as  the  cylindrical  fibres,  the  fasciculi  or  bundles,  and  the 
muscle  sheath  are  all  united  by  connective  tissue,  so  also  is 
the  tendon  united  to  the  connective  tissue  elements  in  the 
muscle  belly,  and  to  the  sarcolemma  as  well.  By  means  of 
maceration  the  tendinous  origin  may  be  traced  through 
the  muscle  to  the  tendinous  insertion.  It  forms  with  the 
connective  tissue  elements  part  of  the  elastic  system  of  the 


PRINCIPLES  3 

muscle.     It  is  not  usual  to  find  tendon  unless  there  is  an 

insertion  into  bone  ;    thus  it  is  not  found  in  connection 

with  the  muscles  of  the  tongue,  where  contractile  power  is 

brought   into   play   throughout   the  whole  length   of   the 

muscle.     By  means  of  tendon  the  force  of  a  powerful  muscle 

is  concentrated  on  a  small  area,  and  in  addition  space  is 

economized  and  limb  conformity  maintained,  as  in  the  case 

of  the  pectoralis  major  and  latissimus  dor  si  of  the  upper 

limb.      Leverage  is   also   improved,  as  is  seen  in  the  long 

tendons   of  the  hands  and   feet.      Thus  the  muscle  can 

act  from  a  distance  though  placed  near  the  axis  of  the 

body  most  suitable  for  nutrition  and  innervation.     Where 

flexibility  is  not  essential,  as  in  the  legs  of  birds,  we  have  a 

bony  process  between  the  ends  of  muscle  and  the  bone  to  be 

moved.     Where  the  muscle  is  inserted  into  bone  without 

the  intervention  of  tendon  we  have  power  at  the  expense 

of  velocity  of  action.     Such  examples  are  not  common  in 

the  economy  of  the  body.     By  the  intervention  of  tendon 

between  the  muscle  or  motor  force  and  the  part  to  be 

moved,  and  especially  owing  to  its  elastic  property,  the 

muscle  is  able  by  this  means  to  accommodate  itself  to  any 

required  movement  at  its  fulcrum  or  centre  of  motion. 

A   striking   example   of   tendon   or   non-contractile   tissue 

limiting  the  length  and  action  of  muscular  or  contractile 

tissue  to  the  amount  of  motion  necessary  to  be  effected,  is 

seen  in  the  sterno-thyroidei  of  the  giraffe,  where  alternation 

of  these  structures  is  present.     In  this  way  the  action  of  these 

muscles  in  drawing  down  the  larynx  and  hyoid  is  limited, 

since  they  would  be  drawn  a  considerable  distance  down 

the  neck  were  tendinous  material  not  interposed. 

In  general  it  may  be  stated  that  the  greater  the  fleshy 
nature  or  "  muscularity "  of  a  muscle,  the  greater  its 
stability  and  strength.  To  be  convinced  of  this  one  has 
only  to  compare  the  forearm  of  the  "  selected  "  *  marsupial 
— the  wombat — -perhaps  the  most  muscular  animal  amongst 
the  mammalia,  with  the  forearm  of  a  carnivorous  marsupial 
like  the  Tasmanian  devil,  or  with  that  of  a  vegetable  eater 

*  Used  in  the  sense  of  selection  of  the  fittest. 


4  THE    ACTION    OF    MUSCLES 

like  the  kangaroo.  In  the  Tasmanian  devil  four  digits  only 
are  present  and  tendinous  substance  is  well  defined  even 
in  the  flexor  belly,  and  in  the  kangaroo  associated  with 
a  non-opposable  thumb  is  a  comparatively  tendinous 
condition  of  the  forearm  muscles,  which  is  especially  seen 
in  connection  with  the  brachio-radialis  (supinator  longus). 
It  would  seem  as  if  the  necessity  which  evolved  the 
"  erect  "  posture  in  the  kangaroo  and  its  independence  of 
the  upper  limb  for  support  was  for  some  unknown  reason 
stayed.  This  marsupial  forms  an  interesting  comparison 
as  regards  fore  limb  and  brain  with  man.  Whether  a  muscle 
is  largely  fleshy  in  character,  or  partly  muscular  and  partly 
tendinous,  or  mainly  tendinous,  has  an  important  bearing 
on  recovery  in  poliomyelitis,  and  especially  in  old  cases. 
This  condition  helps  to  explain  why  fleshy  muscles  like 
those  of  the  abdomen,  psoas,  muscles  of  the  neck,  and 
buttock  recover  quickly  if  seen  early  and  re-educated  on 
scientific  lines,  and  why  the  muscles  of  the  leg  are  amongst 
those  most  difficult  to  recover.  It  is  worth  bearing  in 
mind  that  the  tibialis  anticus,  which  is  frequently  affected, 
is  tendinous  for  more  than  half  its  actual  length. 

III.    Relation  of  Bone  to  Muscle 

By  means  of  bones  and  joints  the  results  of  muscular 
action  are  produced  and  adjusted,  and  the  shapes  and 
lengths  of  bones  bear  a  relation  to  the  motions  performed. 
Bone  is  dominated  by  muscular  function,  for  that  it  is 
called  into  being,  with  the  disappearance  of  that  necessity 
so  also  disappears  the  bone.  Of  its  subservience  to  muscle 
there  are  numerous  instances  scattered  throughout  the 
animal  world.  Where  extensive  muscular  attachment  is 
required  we  have  a  broadening  of  the  bony  surface,  and  a 
narrowing  or  rotundity  where  such  attachment  is  diminished; 
compactness  or  lightness  of  bone  where  strength  or  other- 
wise is  required  ;  and  bony  ridges  and  projections  to  afford 
leverage.  In  this  respect  one  may  mention  the  roundness 
replacing  the  sharp  tibial  edge  associated  with  an  atrophied 


PRINCIPLES  5 

tibialis  anticus  ;  the  bony  prominence  at  the  junction  of 
the  upper  and  middle  third  of  the  tibia  in  koala  for  the 
attachment  of  the  semitendinosus  and  semimembranosus  ; 
the  development  of  ribs  with  specialization  of  pulmonary 
respiration  ;  and  the  relatively  large  development  in  erect 
man  of  the  great  trochanter  for  muscular  attachment.  It 
is  the  length,  size,  and  "  tonicity"  of  the  muscles  that 
maintain  the  normal  length  and  size  of  the  bones,  and  not 
the  reverse,  as  is  so  often  and  erroneously  taught.  The 
quantity  of  motion  in  a  joint  is  regulated  by  the  power  of 
contraction  and  relaxation  of  the  muscles  which  act  on 
it.  In  connection  with  a  joint  such  as  the  knee,  with  an 
extensive  range  of  movement,  the  muscles  are  long,  in 
contrast  to  those  of  the  spine  where  motion  is  limited. 
The  joint  must  accommodate  itself  to  the  necessities  of 
muscular  function. 

IV.    Origin  and  Insertion  of  Muscle 

The  origin  of  a  muscle  represents  its  fixed  point  or  basis 
for  action,  and,  speaking  generally,  is  of  the  two  attachments 
the  one  nearer  to  the  spinal  axis  of  the  body.  The  insertion 
is  the  movable  point  where  the  effects  of  muscular  action  are 
produced,  and  is  generally  farther  from  the  axis  of  the  body 
than  the  origin.  It  represents  the  point  at  which  the  power 
(P)  of  the  lever  acts.  Many  muscles  are  however  capable  of 
acting  in  a  reverse  way,  as  for  example  the  flexors  and  ex- 
tensors of  the  hip,  knee,  and  elbow.  In  this  case  what  is 
usually  known  as  the  insertion  is  the  fixed  point  and  farther 
from  the  axis,  and  what  is  usually  known  as  the  origin 
becomes  the  insertion  and  nearer  to  the  axis  of  the  body. 
In  general,  both  the  origin  and  insertion  of  muscles  are 
from  bone  or  cartilage,  although  this  is  not  always  so,  as 
for  example  the  lingual  muscles,  palmaris  longus,  and  lum- 
bricales.  The  insertion  of  muscle  is  usually  nearer  to  the 
fulcrum  or  centre  of  motion  than  the  origin,  even  where  the 
insertion  represents  P  of  a  lever  of  the  first  order  (stability) 
as  in  the  occipito-atlantal  joint,  the  second  order  (strength) 


6  THE    ACTION    OF    MUSCLES 

as  in  the  insertion  of  the  tendo  achillis  at  the  os  calcis,  or 
the  third  order  (velocity),  which  is  the  most  common  in  the 
body,  as  in  the  flexors  and  extensors  of  the  fingers  and  toes. 
Occasionally,   however,   the   insertion   of   the  muscle  is 
farther  from  the  centre  of  motion  than  the  origin,  as  is  seen 
in  the  deltoid  and  coraco-brachialis.     These  two  muscles 
are  examples  of  the  third  order  of  levers,  and  the  effects  of 
the  position  of  insertion  are  somewhat  similar  to  the  usual 
arrangement  in  which  the  origin  is  farther  from  the  centre 
of  motion,  since  action  is  produced  with  a  minimum  effort. 
The   accurate  knowledge  of  the  origin  and  insertion  of   a 
muscle  is  essential  in  determining  its  action.     This  applies 
however   much   more   particularly   to   the   insertion   of   a 
muscle  than  to  its  origin.     It  is  to  this  that  the  student's 
attention  should  be  directed  when  dissecting  the  muscular 
system.     By  observing  the  exact  attachment  of  insertion 
he  will  be  able  to  determine  the  function,  but  it  must  be 
remembered  that,  owing  to  the  varied  construction  of  joints 
for  purposes  of  motion,  the  insertion  of  a  muscle  is  as  a 
rule  much  less  easily  displayed  than  the  origin,  which  is 
usually   coarser  and  simpler.       Ocasionally,  however,  the 
origin  of  a  muscle  is  more  difficult  to  display  than  the 
insertion,  as  in  the  case  of  the  brachialis.     It  is  owing  to 
the  failure  to  recognize  the  importance  of  the  part  played 
by  muscle  insertion  in  determining  action,  that  such  ignor- 
ance is  displayed  when  the  results  of  the  re-education  of 
muscles,  after  poliomyelitis  or  nerve  division,  are  demon- 
strated.   When  such  muscles  are  treated  on  sound  biological 
and  mechanical  lines,  re-educated  from  a  position  of  "  zero  " 
or    minimum    function,    surprising    results    are    obtained. 
As  these  do  not  coincide  with  the  teachings  of  past  cen- 
turies,  they  are  falsely  ascribed  to  the  actions  of  other 
muscles,  which  from  the  position  of  their  insertion  could 
not  possibly  produce  the  results.      Bearing  in  mind  the 
insertion  of  muscle  and  the  effects  produced  by  volition, 
one  should  not  mistake  the  action  of  a  re-educated  muscle 
for  that  of  some  other  muscle,  which,  by  its  insertion,  is 
disposed  to  produce  the  opposite  effect. 


PRINCIPLES  7 

V.    Ligaments 

It  would  scarcely  seem  necessary  to  state  that  ligaments 
do  not  produce  motion  of  a  part,  but  exist  in  relation  to  a 
joint  for  the  purposes  of  maintaining  the  necessary  distance 
between  its  component  parts.  Owing  to  their  elasticity  they 
can  adapt  themselves  to  altered  relations  of  the  components 
of  the  joint,  which  alterations  are  the  result  of  muscular 
contraction  in  response  to  a  need  or  wish.  They  are  passive 
agents  under  the  influence  of  muscle.  The  muscles  sur- 
rounding joints  are  much  more  important  factors  in  strength- 
ening them  than  the  ligaments  connecting  the  components 
of  the  articulation.  Ligaments  such  as  the  collateral  tibial 
(internal  lateral)  of  the  knee  are  liable  to  rupture,  while 
muscles,  owing  to  their  power  of  contraction  and  relaxation, 
have  greater  power  of  accommodation  to  alterations  of  the 
relations  of  the  components  of  the  joint. 

In  re-educating  a  "  paralysed  "  quadriceps  we  find  that 
the  patient  can  elevate  the  lower  limb  off  the  bed  with 
the  knee  extended  when  lying  on  the  opposide  site,  before 
he  can  complete  the  maximum  or  ioo  units  of  work,  eleva- 
tion of  the  limb  with  the  knee  extended  when  lying  on  the 
back.  In  the  course  of  a  public  discussion  of  this  action  I 
heard  it  stated  that  the  elevation  on  the  side  was  dependent 
on  the  stiffening  action  of  the  lateral  ligaments,  as  though 
the  ligaments  could  cause  movement.  Again,  it  is  often 
erroneously  stated  that  talipes  valgus  or  flat  foot  depends 
primarily  on  a  yielding  of  ligaments,  whereas  the  basic 
factor  is  muscular,  an  alteration  in  the  equilibrium  between 
the  inverters  and  everters  of  the  foot,  dependent  on  a 
paresis  or  paralysis  of  the  former.  As  throwing  light  on 
the  origin  and  place  in  the  animal  economy  of  ligamentous 
bands  one  need  only  refer  to  the  comparative  anatomy  of 
the  ligamentum  teres,  or  of  the  lateral  ligaments  of  the 
knee.  The  external  represents  the  tendon  of  origin  of  the 
peroneus  longus  when  it  extended  to  the  femur,  and  the  in- 
ternal represents  the  insertion  of  the  adductor  magnus 
when  it  extended  to  the  tibia.     From  a  study  of  correlations 


8  THE    ACTION    OF    MUSCLES 

it  would  appear  that  the  long  head  of  the  biceps  brachii, 
which  prevents  impaction  of  the  head  of  the  humerus 
during  abduction,  will  ultimately  be  represented  by  an 
intra-articular  ligament,  the  origin  of  the  muscle  becoming 
solely  coracoid. 

VI.    Pulleys,  Sesamoids,  and  Levers 

In  the  application  of  muscular  forces  throughout  the 
body  nature  is  ever  seeking  advantages  to  effect  velocity 
and  force  of  action  with  the  minimum  expenditure  of 
energy.  The  shape  of  the  muscle,  the  arrangement  of  its 
component  fibres,  the  course  of  the  tendon  relative  to  that 
of  the  fleshy  belly,  its  position  of  insertion,  are  all  modifying 
factors  ;  and  it  has  been  truly  said  that  the  human  body 
has  formed  the  basis  of  innumerable  contrivances  used  by 
mechanical  engineers  for  the  conservation  of  force.  By 
means  of  the  fixed  single  pulley  the  direction  of  force  of 
a  muscle  is  altered.  There  is  a  mechanical  gain,  and  any 
loss  of  force  of  action  from  friction  is  lessened  by  the  use 
of  a  synovial  sheath  or  bursa.  The  struggle  of  muscles 
for  attachment  undoubtedly  called  the  pulley  into  being. 
By  its  means  a  muscle  may  for  convenience  be  attached 
at  one  part  of  a  limb  while  its  action  is  being  produced 
in  a  different  portion.  Good  examples  are,  the  cartilaginous 
loop  for  the  superior  oblique  on  its  way  to  the  eyeball — 
the  fibrous  loop  at  the  hyoid  bone  for  the  digastric  ;  the 
peroneus  longus  looping  round  the  outer  malleolus  on  its 
passage  to  the  inner  side  of  the  foot  ;  and  the  obturator 
internus  which,  though  arising  in  the  pelvis,  is  enabled  to 
act  on  the  upper  end  of  the  femur  by  means  of  a  groove  on 
the  inner  surface  of  the  ischial  tuberosity. 

The  more  parallel  the  termination  of  a  muscle  is  to  the 
axis  of  the  bone  into  which  it  is  inserted  the  weaker  its 
action — 'the  maximum  effort  is  obtained  when  the  line  of 
its  resultant  forms  a  right  angle  with  the  bone  into  which 
it  is  inserted.  Thus  when  the  elbow  is  extended  or  acutely 
flexed  the  moment  of  force  of  the  brachialis  is  at  its  weakest 


PRINCIPLES  9 

— the  greatest  moment  corresponds  to  the  position  when 
the  forearm  is  at  a  right  angle,  the  brachialis  then  acting 
almost  perpendicularly  on  the  ulna.  Thus  in  testing  for 
recovery  in  a  "  paralysed  "  brachialis  the  forearm  should  be 
passively  brought  to  the  right  angle  with  the  patient  lying 
down.  Unfortunately  the  test  usually  given  to  a  weakened 
brachialis  is  to  ask  it  to  do  ioo  units  of  work ;  the  patient 
is  asked  to  bring  the  hand  to  the  mouth  while  sitting  or 
standing,  with  the  elbow  extended  and  the  hand  at  the  side. 
Notable  examples  in  the  body  by  which  this  principle  of 
the  pulley  is  effected  are  the  patella,  through  which  the 
main  force  of  the  quadriceps  acting  through  the  ligamentum 
patellae  is  increased  by  being  raised  from  the  centre  of 
motion  at  the  knee  ;  and  the  sublimis  and  profundus  tendons 
of  the  fingers  where  each  in  turn  acts  as  a  patella  to  the 
other.  I  have  little  doubt  also  that  this  is  the  reason  why 
the  latissimus  dorsi  near  its  termination  passes  over  the 
lower  angle  of  the  scapula. 

A  very  interesting  example  of  the  production  of  an 
artificial  pulley  is  seen  in  connection  with  the  above  action 
of  the  flexores  sublimis  and  profundus.  As  is  well  known 
the  position  of  the  hand  for  a  strong  flexion  grip  is  that  of 
extension  (dor si-flexion)  at  the  wrist  joint ;  and  when  in 
the  case  of  a  diseased  wrist  ankylosis  is  the  desideratum, 
this  is  the  position  of  greatest  utility.  The  grip  becomes 
weaker  and  flexion  power  becomes  lessened,  as  we  approach 
the  position  of  acute  flexion.  This  important  point  is  made 
use  of  in  the  re-education  of  the  flexors  in  a  case  of  median 
or  combined  median  and  ulnar  paralysis.  The  position 
of  dorsi-flexion  of  the  wrist  is  independent  of  the  muscles 
which  move  the  fingers.  It  is  caused  by  the  contraction  of 
the  two  radial  extensors  and  the  extensor  carpi  ulnaris, 
with  the  relaxation  of  the  flexor  carpi  radialis  and  flexor 
carpi  ulnaris.  The  result  of  this  position  is  that  the  flexores 
sublimis  and  profundus  tendons  are  enabled  to  enter  the 
hand  in  such  a  way,  that  the  portion  in  the  forearm  forms 
an  angle  with  the  manual  portion,  the  wrist  becoming  a 
fixed  pulley  over  which  the  tendons  play.      In  a  case  of 


io  THE    ACTION    OF    MUSCLES 

median  and  ulnar  nerve  repair  after  complete  division  in 
the  arm,  I  found  during  the  process  of  re-education,  that 
although  the  patient  flexed  readily  in  the  dorsi-flexed  posi- 
tion ;  yet  when  the  wrist  was  in  the  position  of  equilibrium 
as  regards  the  flexors  and  extensors,  the  power  of  contraction 
of  the  fingers  became  lessened,  and  when  the  wrist  was  bent 
the  patient  was  unable  to  flex  the  fingers  even  to  a  slight 


EXTENDERS 
OF 


POWERS Ur~U^L FULCRUM 


WEIGHT 


extent.  The  action  of  the  lumbricales  (the  flexors  of  the 
metacarpo-phalangeal  joints  of  the  fingers)  which  take  their 
origins  from  the  profundus  tendons  would  be  similarly 
affected. 

In  the  human  body  the  bones  which  give  attachment  to 
muscles,  the  muscles  by  which  motion  is  produced,  and  the 
joints  by  which  the  bones  are  enabled  to  move  on  one  another, 
are  found  to  conform  to  a  system  of  levers  arranged  in  three 


PRINCIPLES  ii 

orders.  F  represents  the  fulcrum  or  centre  of  motion  at 
the  joint,  P  the  power  of  muscle  contraction  applied  at  the 
insertion  of  the  muscle,  W  the  resistance  to  be  overcome. 
In  a  lever  of  the  first  order  the  fulcrum  lies  between  the 
weight  to  be  moved  and  the  power.  A  good  example  of 
this  order  is  found  in  the  articulation  of  the  head  on  the 
atlas.  Thus  in  extension  of  the  head  the  power  is  applied 
by  the  extensors  of  the  head,  the  fulcrum  is  in  the  middle 


WEIGHT 


Fig.  3. 

at  the  occipito-atlantal  joints,  and  the  weight  to  be  lifted 
is  anterior.  The  feature  of  this  arrangement  is  stability, 
but  it  must  not  be  supposed  that  this  stability  depends  on 
the  bony  arrangements  and  not  on  the  muscle.  In  a  case 
of  poliomyelitis  affecting  the  flexors  the  head  is  drawn 
backwards  on  the  spine,  and  in  unconsciousness  the  head 
tends  to  fall  forwards.  Another  good  example  is  seen 
when  we  lift  the  foot  off  the  ground,  and  point  the  toes 
downwards  by  extending  the   ankle   (fig.   2).      Here   the 


12  THE    ACTION    OF    MUSCLES 

fulcrum  or  centre  of  motion  is  the  ankle,  the  power  the 
attachment  of  the  tendo  achillis  at  the  os  calcis,  and  the 
weight  or  resistance  the  front  of  the  foot. 

In  a  lever  of  the  second  order  W  lies  between  P  and  F. 
This  variety  is  not  common.  It  is  the  lever  of  power  as 
compared  with  velocity — the  power  arm  being  longer  than 
the  weight  arm.  The  best  example  in  the  body  is  seen 
(fig.  3)  when  a  person  stands  on  tip-toes  and  supports  the 
body  on  the  ball  of  the  toes,  which  is  the  fulcrum — the 
resistance  or  weight  is  that  of  the  body  transmitted  through 
the  tibia  on  the  astragalus — and  the  power  is  applied  to  the 
os  calcis  or  calcaneus  by  the  tendo  achillis. 

In  the  third  order,  the  common  variety  of  lever,  P  lies 
between  W  and  F.     It  is  the  lever  of  velocity  as  compared 

BRACHIALIS 
WBI&HT 


FULCRUM 


with  power,  for  the  power  has  a  shorter  arm  than  the  weight. 
A  good  example  is  seen  (fig.  4)  in  the  action  of  the  brachialis 
in  bending  the  elbow  with  a  weight  in  the  hand.  The  elbow 
joint  is  the  fulcrum  or  centre  of  motion.  The  power  is 
applied  at  the  insertion  of  the  brachialis  into  the  coronoid 
process  of  the  ulna,  and  the  weight  to  be  lifted  is  the 
forearm  and  hand. 

VII.  Form  and  Arrangement  of  Muscle 
The  muscles  of  the  body  present  a  great  variation  in  size 
and  shape.  They  may  be  broad  or  narrow,  long  or  short, 
round  or  flat,  thick  or  thin.  Speaking  generally,  in  the  case 
of  the  limbs  the  superficial  muscles,  such  as  the  hamstrings, 
are  longer  than  the  deep,  and  the  deep  muscles  are  the 


PRINCIPLES  13 

broader,  as  seen  in  the  case  of  the  pronator  quadratus  and 
popliteus.  In  the  trunk,  as  is  evidenced  by  the  greater 
area  for  attachment,  the  muscles  are  broader  than  in  the 
limbs.  There  is  also  a  great  variability  throughout  the 
muscles  of  the  body  in  the  arrangement  of  the  true  con- 
tractile fibres  relative  to  the  tendons  to  which  they  are 
attached.  It  is  not  possible  to  find  in  the  body  a  muscle 
whose  fibres  run  parallel  to  each  other  from  the  origin  to 
the  insertion.  Perhaps  the  nearest  approaches  to  this  recti- 
lineal type  are  the  pronator  quadratus  and  the  thyro-hyoid. 
With  this  arrangement  too  much  muscular  energy  is  ex- 
pended to  produce  a  desired  result,  since  the  line  of  the 
resultant  of  forces  of  the  muscle  is  the  same  in  the  tendon 
as  in  the  fleshy  belly.  It  is  interesting  to  note  that  though 
the  pectineus  approaches  the  rectilineal  type,  the  expenditure 
of  energy  is  lessened  and  velocity  improved,  owing  to  the 
fact  that  the  planes  of  origin  and  insertion  are  not  on  the 
same  level  but  intersect. 

Speaking  generally  the  arrangement  in  the  skeletal  muscles 
is  such  that  the  fibres  do  not  go  straight  from  origin  to  in- 
sertion, but  are  directed  obliquely.  By  this  obliquity,  as  is 
shown  in  the  action  of  the  intercostal  muscles,  is  produced  a 
more  rapid  action  with  a  smaller  contraction,  and  a  lessened 
expenditure  of  energy,  than  if  the  fibres  were  continued  in  a 
straight  line  to  the  tendinous  insertion.  By  this  arrange- 
ment also  liberty  of  limb  motion  is  freely  obtained.  The 
nearer  the  deviation  of  the  muscle,  relative  to  the  direction 
of  its  tendon  of  insertion,  approaches  the  right  angle,  the 
less  is  the  contraction  necessary  to  produce  the  desired 
effect.  The  oblique  arrangement  of  fibres  is  well  exemplified 
in  muscles  like  the  peronei  where  the  fibres  are  attached  to 
one  side  of  a  tendon  like  the  plumes  of  a  pen.  This  is  the 
so  called  half-penniform  arrangement ;  or  we  may  have  an 
additional  course  of  oblique  fibres,  which  converge  obliquely 
on  each  side  to  a  single  medial  tendon,  by  which  arrange- 
ment their  power  is  increased.  This  is  the  complete  penni- 
form  or  bipenniform  arrangement,  and  the  best  example  in 
the  body  is  the  rectus  femoris.     In  the  case  of  the  deltoid 


14  THE   ACTION    OF   MUSCLES 

the  belly  is  strengthened  and  action  improved  by  the  inter- 
position in  the  belly  fibres  of  tendinous  bands.  In  triangular 
muscles  the  fibres  arise  over  a  broad  origin,  but  the  insertion 
is  a  narrow  one.  Good  examples  of  this  are  the  pectoralis 
major — temporal — and  the  gluteus  minimus.  By  this  ar- 
rangement powerful  muscular  action  can  be  concentrated 
on  a  narrow  area. 

VIII.    The  Evolution  of  Muscular  Action  :    Muscle 
Re-education 

It  is  customary  for  us  to  speak  of  the  action  of  any  given 
muscle  as  though  it  represented  a  single  entity,  forgetting 
that  the  muscles  of  man  are  "selected"  results  following 
struggles  which  have  extended  over  many  ages.  Thus  we 
speak  of  a  flexor  or  extensor  of  a  joint,  as  though  these  terms 
conveyed  everything  necessary  to  explain  function. 

My  attention  was  first  drawn  to  this  question  more  than 
ten  years  ago  by  studying  the  action  of  the  quadriceps, 
deltoid,  and  brachialis  muscles  in  cases  of  poliomyelitis. 
In  this  disease  examples  of  quadriceps  paralysis  were  met 
with  in  which  the  patient  was  unable  to  stand,  or,  when 
lying  in  bed  to  raise  the  heel  with  the  knee  extended  ; 
however,  when  lying  on  the  side  opposite  to  that  which  was 
affected,  and  the  knee  then  being  flexed,  it  was  found  that 
the  leg  could  be  extended  with  ease.  Because  a  patient  is 
unable  to  raise  the  heel  off  the  ground  with  the  knee  straight 
when  sitting  on  a  chair — is  unable,  that  is,  to  do  ioo  units 
of  work — we  are  not  justified  in  calling  the  quadriceps 
"paralysed."  On  tthe  same  reasoning  the  quadriceps 
tested  with  the  patient  in  bed  and  with  the  knee  acutely 
flexed  might  be  regarded  as  normal,  since  it  can  perform 
the  function  of  the  quadriceps  as  given  in  the  text-books, 
that  is  to  say,  extend  the  knee. 

In  the  case  of  the  deltoid  it  is  not  infrequent  in  connection 
with  poliomyelitis  or  trauma  to  find  a  patient  who  is  unable 
to  elevate  the  arm  when  standing  or  sitting  erect.  The 
deltoid  is  condemned  as  hopeless  for  recovery,  since  it  has 
failed  to  respond  to  treatment  by  massage  and  electricity. 


PRINCIPLES  15 

Yet  such  a  patient  if  lying  fiat  on  the  back  may  be  able  to 
raise  the  upper  limb  above  the  head  with  ease,  and  by  gradual 
elevation  to  the  erect  posture  may,  within  a  few  months,  be 
able  to  raise  the  limb  above  the  head  when  standing  erect. 
Or  we  may  find  a  patient  with  a  paralysed  brachialis  who  is 
unable  when  tested  sitting  or  standing  erect  to  bring  the  hand 
of  the  affected  side  to  the  mouth.  But  the  same  patient 
when  lying  on  the  back  with  the  limb  supported  by  a  pillow 
in  the  manner  which  I  will  subsequently  indicate  may  be 
found  able  to  flex  the  forearm  readily  from  full  elbow  exten- 
sion. These  phenomena  admit  in  my  opinion  of  only  one 
explanation,  that  the  disease  or  injury  is  revealing  functional 
stages  in  the  evolution  of  these  muscles.  They  show  that 
muscle  action  is  a  complex  function,  one  made  up  of  several 
separate  activities,  and  hence  the  term  "paralysis"  of 
muscles  is  realty  referable  to  the  loss  of  some,  not  necessarily 
all,  of  their  functions.  The  recovery  like  the  loss  follows  in 
an  ancestral  or  evolutionary  sequence. 

Frequently  one  hears  the  term  "  irreparable  damage  " 
applied  to  central  nerve  cells  in  cases  of  poliomyelitis. 
Such  a  term,  unless  qualified,  is  not  only  meaningless  but 
misleading.  So  called  "  irreparable  damage  "  can  only  be 
recognized  by  the  degree  of  muscle  "  paralysis  "  present, 
and  this  depends  upon  the  nature  of  the  test  applied  to  the 
muscle.  Thus  "irreparable  damage"  might  be  applied 
to  the  cell  condition  when  the  quadriceps  failed  to  contract 
sufficiently  to  enable  the  patient  to  elevate  a  lower  limb  off 
the  bed  in  one  piece,  yet  such  a  quadriceps  tested  from 
"  zero  "  might  show  every  other  function  to  be  present. 
"  Irreparable  damage  "  and  "  paralysis  "  are  really  referable 
not  to  the  muscle,  but  only  to  the  loss  of  part  of  its  function  ; 
the  restoration  of  which  follows  a  biological  law.  So  called 
"irreparable  damage"  must  be  judged  by  the  loss  of  all 
functions  of  a  muscle — all  must  be  tested,  not  some  or  any. 
Thus  when  we  speak  of  recovery  in  a  deltoid  or  a  quadriceps 
it  is  necessary  to  define  exactly  the  extent  of  the  recovery. 
Do  we  refer  to  100  units  of  work — the  work-power  of  the 
corresponding  normal  muscle  of  the  other  limb — or  to  only 


16  THE    ACTION    OF    MUSCLES 

50  ?  The  above  method  of  testing,  which  is  based  on  a 
scientifically  directed  volition,  is  the  only  real  test  for  muscle 
recovery.  It  is  the  only  one  which  takes  into  account  the 
contracting  force  and  the  relaxing  opponent.  Do  medical 
men  seriously  believe  that  an  externally  applied  electric 
current  has  the  power  of  eliciting  functional  entities  of  a 
muscle  or  of  discriminating  between  them  ?  It  is  this 
volitional  test  which  should  primarily  tell  us  whether  an 
operation  on  a  motor  nerve  suspected  of  injury  should  be 
performed  or  not. 

The  assumption  of  the  erect  posture  has  had  a  dominating 
influence  on  the  muscles  of  the  human  body,  and  the  study 
of  muscular  action  throughout  the  mammalia  shows  that  the 
orthograde  functions  have  been  superimposed  on  muscles 
adapted  originally  for  plantigrade  motion  ;  new  muscles  have 
not  been  called  into  being.  Although  Charles  Bell  taught 
us  that  the  anterior  cord  presides  over  muscular  action,  and 
Marshall  Hall  that  movement  can  occur  reflexly  as  well  as 
from  volition,  a  study  of  cases  of  infantile  paralysis  in  man 
also  demonstrates  the  fact  that  the  anterior  cord  presides 
not  merely  over  "  muscular  action,"  but  also  recognizes  the 
components  of  which  a  function  is  made  up,  and  that  these 
cell-controlled  components  of  a  purposive  movement  always 
bear  a  definite  sequence  one  to  another. 

The  action  of  the  quadriceps  is  vastly  different  in  platypus 
and  in  man.  The  quadriceps  in  platypus  corresponds  to  the 
anatomical  test  of  extension  of  a  flexed  knee,  but  that  is  a 
distinct  function  from  that  of  a  quadriceps  which  will  allow 
of  the  orthograde  posture.  The  quadriceps  of  the  ape  has 
a  more  complex  function  than  that  of  the  platypus,  and  so 
similarly  has  man's  compared  with  the  anthropoid.  A 
patient  who  can  raise  the  heel  off  the  ground  when  sitting 
with  the  knee  extended  will  be  able  to  extend  the  acutely 
flexed  knee  in  bed  ;  but  the  patient  who  can  do  the  latter 
need  not  necessarily  be  able  to  do  the  former.  When,  there- 
fore, we  are  told  that  the  quadriceps  is  paralysed  merely 
because  the  patient  is  unable  to  raise  the  heel  of  the  extended 
leg  off  the  ground,  we  are  told  something  which  is  biologically 


PRINCIPLES  17 

untrue.  This  is  a  question  apart  altogether  from  volition, 
since  in  infantile  paralysis  we  are  dealing  generally  with 
a  disease,  in  which  cerebration  is  unaffected.  The  koala 
shows  us  a  typical  exhibition  of  deltoid  function  amongst 
the  marsupials.  Compared  with  the  deltoid  of  the  wombat 
that  of  the  koala  has  become  differentiated  from  the  outer 
pectoral,  trapezius,  and  brachio-radialis  (fig.  9).  Although 
the  koala,  supporting  himself  with  one  hand  in  the  fork  of 
a  tree,  can  reach  for  his  meal  of  eucalyptus  leaves,  that  is 
a  different  matter  from  the  ability  to  raise  the  arm  when 
the  orthograde  posture  is  assumed.  Again,  a  study  of  the 
anthropoids  at  any  menagerie  shows  with  what  reluctance 
they  dispense  with  the  fore  limb  as  a  means  of  support. 

The  ape  prefers  the  knee  slightly  bent,  with  the  balance 
afforded  by  one  or  both  fore  limbs.  To  assume  the  ortho- 
grade posture  is  an  effort,  and  it  is  a  still  greater  one  while 
in  the  upright  position  to  raise  the  fore  limb  above  the  head. 
The  stiffening  of  the  knees  by  the  quadriceps— which  has 
enabled  man  to  stand  and  walk — and  the  ability  not  only 
to  dispense  with  the  fore  limb  for  support,  but  to  elevate 
it  when  erect  above  the  head,  are  late  acquisitions  in  man's 
evolution,  and  are  hence  unstable. 

It  is  such  observations  as  these  that  have  induced  me  to 
formulate  the  evolutionary  law  of  muscle  function.  The 
particular  functions  of  any  muscle  are  the  result  of  the 
evolutionary  history  of  that  muscle. 

Compared  with  embryology,  which  gives  us  an  imperfect 
picture  of  man's  evolution  from  the  point  of  view  of  structure 
correlated  with  function,  comparative  anatomy  not  only 
gives  a  connected  history  of  the  past  phases,  but  often  points 
the  directions  in  which  man's  future  physical  evolution  may 
progress.  For  example,  it  will  I  think  be  conceded  that 
inversion  and  eversion  of  the  human  foot  are  diminishing, 
since  the  foot  is  not,  as  in  koala,  provided  with  an  opposable 
hallux  ;  also  that  the  tibia  is  the  dominant  bone  of  the  leg, 
and  that  the  fibula  is  disappearing.  The  fibula  in  the  kan- 
garoo, from  the  point  of  view  of  function,  is  non-existent, 
having  become  approximated  to  the  tibia  ;  reminding  one  of 
2 


18  THE    ACTION    OF    MUSCLES 

the  manner  in  which  the  appendix  has  become  fused  with 
the  ileum  in  the  wombat.  In  the  kangaroo  a  struggle  exists 
round  the  ankle,  as  elsewhere,  between  individual  muscles, 
not  only  for  position  but  for  existence.  The  kangaroo's  foot 
can  be  regarded,  then,  as  of  especial  value  in  enabling  us 
to  recognize  that  certain  muscles  are  "  survival  results." 

Even  if  the  "  paralysed  "  patient  be  treated  at  a  stage 
of  the  disorder  when  some  surgical  interference  is  necessary, 
the  comparative  method  of  treatment  should  still  dominate 
the  surgeon's  action,  whether  the  method  be  the  "  strength- 
ening of  the  weak  "  by  muscle  or  nerve  transplantation,  or 
the  M  weakening  of  the  strong,"  as  by  tendon  lengthening 
or  division.  If  we  are  utilizing  a  tibial  or  peroneal  muscle 
for  grafting,  it  is  important  to  know  which  tibial  or  which 
peroneal  is  the  more  useful  in  the  body  economy.  Simi- 
larly, if  we  are  diminishing  the  power  of  eversion  because 
the  tibials  are  weak,  or  inversion  because  the  peronei  are 
damaged.  The  results  obtained  from  nerve  and  muscle 
grafting  in  paralysis  have  so  far  been  disappointing,  and  for 
the  reason  that  muscle  function — the  important  factor — -has 
usually  received  such  scant  consideration.  It  seems  ridi- 
culous to  graft  a  biceps  femoris  or  other  hamstring  to  the 
quadriceps  and  expect  it  to  restore  extension — that  is, 
to  repeat  the  biological  history  of  the  function  of  that 
muscle — -unless  we  have  a  clear  idea  of  the  entities  of  which 
that  function  is  composed.  Again,  presuming  we  have 
reinforced  the  circumflex  nerve  of  a  paralysed  deltoid,  it 
is  surely  too  much  to  expect  that  nerve  impulses  alone  will 
stimulate  the  muscle  to  repeat  in  sequence  the  events  of 
its  evolutionary  history. 

IX.    Muscle  Rest  :    Zero  Position 

From  the  scant  attention  paid  by  clinicians  to  muscle 
rest  in  diseases  of  the  nervous  system  it  would  appear  that 
rest — and  by  that  is  meant  physiological  rest — as  a  curative 
agent  is  supposed  to  be  unworthy  of  consideration  as  part 
of  treatment.     To  many  it  appears  to  be  of  no  importance 


PRINCIPLES  19 

that  the  muscle  is  really  a  part  of  a  nervous  mechanism. 
The  motor  nerve  and  the  muscle  are  functionally  inter- 
dependent. It  is  true  that  the  source  of  motion  resides  in  the 
muscle,  but  the  cause  of  voluntary  movement  resides  in  the 
nervous  system.  Through  nerves  the  will  power  is  conveyed, 
but  nerves  have  no  power  of  motion.  Both  the  nerve  and 
muscle  are  best  considered  as  parts  of  an  original  unit,  the 
muscle  retaining  the  power  of  contractibility,  of  producing 
motion,  and  the  nerve  retaining  the  power  of  irritability  and 
of  conduction.  In  a  disease  like  poliomyelitis,  where  the 
chief  trouble  falls  on  the  anterior  cornual  cells,  treatment  has 
always  been  directed  towards  maintaining  the  nutrition  of 
muscles  by  means  of  electricity  and  massage,  in  the  hope 
that  the  cells  might  ultimately  recover,  when  the  muscles 
presumably  would  be  in  a  condition  to  resume  function. 
If  the  muscles  under  such  treatment  did  not  recover  no 
fault  was  found  with  principles  of  treatment,  but  it  was 
supposed  that  the  cornual  cells  were  irreparably  damaged. 
The  atrophied  deltoid  with  flattening  of  the  shoulder  and 
a  dangling  upper  limb  were  unfortunate  but  unavoidable 
results. 

If  rest  is  the  basic  treatment  of  inflammation,  and  towards 
this  we  must  suppose  that  nature  is  always  striving,  it  is  clear 
that  the  cornual  cell  can  be  best  rested  through  the  muscle. 
With  constant  irritation  of  the  muscle  by  faulty  position, 
massage  and  electricity,  the  utmost  is  being  done  to  prevent 
recovery  of  the  inflamed  central  nervous  system.  It  is 
interesting  to  find  that  when  we  rest  a  deltoid  and  ask  it 
gradually  to  resume  work  within  functional  limitations,  it 
does  not  waste  as  was  supposed.  The  fallacy  that  we  must 
do  something  to  the  muscle  "  to  maintain  its  nutrition  " 
would  appear  to  be  dying  as  hard  as  the  one  that  by  resting 
a  j  oint  its  liability  to  ankylosis  is  increased.  If  a  motor  nerve 
be  injured,  the  injury  has  also  affected  the  muscle,  and  how 
can  we  expect  recovery  of  the  muscle  after  repair  of  the  nerve, 
if  we  fail  to  rest  the  muscle  ?  Not  only  is  muscle  rest  the 
most  effective  agent  for  repair  of  injury  or  inflammation 
of  either  muscle  itself  or  of  the  nervous  system  with  which  it 


20  THE    ACTION    OF    MUSCLES 

is  connected,  but  the  position  of  rest  is  the  physiological 
basis  for  the  re-education  of  muscle  function.  It  cannot  be 
too  strongly  insisted  on  that  in  injury  of  a  limb,  as  from  a 
bullet  or  shell  wound,  our  first  care,  apart  from  antisepsis, 
etc.,  of  the  wound  itself,  should  be  the  immobilization  of 
muscles.  Future  muscle  function  should  dominate  fixation, 
and  the  sooner  the  limb  is  rested  from  the  point  of  view  of 
its  musculature,  the  greater  the  ultimate  chance  of  utility. 

Effective  rest  of  muscle  should  begin  at  the  time  of  the 
receipt  of  injury.  This  will  minimize  the  necessity  for 
operative  interference  and  give  the  limb  the  best  chance 
should  an  operation  be  performed.  Immediate  protection 
of  muscles  by  effective  rest  is  fundamental  in  the  treat- 
ment of  injury  of  a  limb.  It  is  a  matter  for  surprise  that 
in  muscular  diseases  such  as  "Myasthenia  Gravis"  com- 
plete rest  such  as  is  given  by  a  double  Thomas  splint  seems 
never  to  be  advised. 

What  Constitutes  Muscle  Rest. — A  normal  muscle  cell  is 
possessed  of  these  two  properties,  the  power  of  contraction 
and  the  power  of  relaxation.  The  stimulus  which  causes 
one  set  of  muscles  to  contract  causes  those  which  act  in  an 
opposite  direction  to  relax.  To  use  a  mechanical  simile — 
the  pressure  in  the  contracting  muscle  which  is  producing 
the  volitional  effect  may  be  at  90  degrees,  while  that  of  the 
relaxing  muscle  may  be  only  at  40.  Either  of  these  states, 
contraction  of  a  muscle,  or  elongation  of  its  relaxed  opponent, 
might  be  described  as  an  irritable  state.  The  intermediate 
position,  which  is  that  of  rest  or  equilibrium,  is  not  a  state 
of  inaction,  but  is  an  active  state  in  which  the  opponents 
are  evenly  balanced — the  state  in  which,  to  apply  the  simile, 
the  pressure  in  each  group  stands  equal  at  45  degrees. 
Thus,  if  we  were  resting  the  radio-ulnar  joints  at  which 
the  rotary  movements  of  pronation  and  supination  occur, 
the  position  midway  between  pronation  and  supination, 
with  the  pollex  up  and  the  minimus  down,  would  be  the 
position  of  repose.  If  both  pronators  and  supinators  were 
paralysed,  the  position  of  rest  would  be  this  normal  position 
of  equilibrium  between  the  two  groups. 


PRINCIPLES  21 

If  a  muscle  be  weakened  or  paralysed,  whether  from  injury 
of  muscle,  nerve,  or  central  cell,  it  is  rested  when  its  opponent 
is  in  a  state  of  relaxation  and  elongation  beyond  the  state 
normally  regarded  as  necessary  to  produce  a  condition  of 
equilibrium  with  its  opponent.  In  this  way  we  prevent  a 
weakened  muscle  being  stretched  and  irritated  by  the  con- 
traction of  its  opponent,  and  we  assume  that  the  application 
of  electricity  or  massage  is  not  allowed  to  interfere  with 
recovery.  Thus  in  paralysis  of  the  supinators  of  the  forearm 
the  position  of  rest  would  be  with  the  hand  over-supinated, 
so  as  to  prevent  action  of  the  normal  opposing  pronators. 
In  the  upper  limb  gravitational  force  has  particularly  to  be 
remembered.  If  we  leave  our  paralysed  deltoid,  as  is 
usually  done,  unsupported  with  the  hand  hanging  at  the 
side,  not  only  have  we  not  true  muscular  rest,  but  have  in 
addition  the  weight  of  the  upper  limb  dragging  on  a  weakened 
muscle.  Frequently  so  great  an  eventual  atrophy  results 
that  the  glenoid  cavity  may  be  digitally  explored.  It  is 
inconceivable  that  with  all  these  disabilities  massage  should 
be  advised. 

Since  rest  is  the  basic  treatment  of  inflammation,  then 
only  by  the  "  zero ' '  position — the  position  as  defined  above — 
can  the  door  be  closed  on  all  sources  of  irritation,  and  cord, 
nerve,"  receptive  substance,"  *  and  muscle  be  at  physiological 
rest.  Furthermore,  the  "  zero  "  position  of  rest  is  the  position 
from  which  the  muscle  can  most  effectively  commence  work. 
When  we  ask  a  patient  with  a  deltoid  paralysed  from  polio- 
myelitis to  commence  work,  as  is  usually  done,  when  sitting 
up  with  the  upper  limb  hanging  at  the  side,  we  are  asking 
damaged  cells  to  begin  work  at  the  greatest  disadvantage, 
asking  a  baby  to  walk  before  he  has  learned  to  stand.  We 
must  ask  muscles  to  begin  work  at  "  zero,"  to  commence 
work  by  beginning  with  a  minimum  function  or  at  a  point 
where  their  load  is  at  a  minimum.  Though  we  speak  of 
a  muscle  anatomically  as  being  flexor  or  extensor  we  really 
refer  to  the  maximum  function  of  a  muscle.  The  question 
arises  as  to  the  recognition  of  the  minimum  of  muscular 

*  Existence  of  this  substance  in  muscle  is  still  theoretical. 


22  THE    ACTION    OF    MUSCLES 

function,  for  it  is  only  by  the  recognition  of  the  minimum 
that  the  muscle  may  ultimately  be  coaxed  up  to  the  maxi- 
mum— the  ideal  aimed  at  by  our  treatment.  Thus,  in  re- 
educating the  quadriceps  we  recognize  that  it  is  incorrect  to 
flex  the  knee  beyond  the  point  at  which  extension  is  possible, 
at  which  effort  becomes  manifest — thus  recognizing  the 
cessation  of  the  opposition  of  the  quadriceps  to  its  opponents. 
The  treatment  for  the  re-education  of  a  paralysed  muscle 
may  be  summed  up  as  the  encouragement  of  voluntary 
muscular  movements  within  functional  limitations.  We 
begin  at  "  zero,"  and  although  we  may  think  that  the 
amount  of  work  at  this  minimum  is  slight,  we  must  re- 
member that  it  really  represents  the  maximum  function 
of  the  muscle  for  the  time  being,  and  as  such  may  soon 
become  exhausted.  In  the  same  way,  the  normal  in- 
dividual would  soon  tire  if  asked  to  continue  flexion  and 
extension  at  the  elbow  joint  for  some  time,  and  to  the 
full  extent. 

X.    Chronic  Muscle  Shortening  :    Contracted  Muscle 

Contraction  or  chronic  shortening  of  muscle  is  a  secondary 
result  of  the  unopposed  volitional  contraction  of  a  muscle 
or  group  of  muscles.  The  muscle  cell  has  the  double  property 
of  contraction  and  relaxation.  Ordinarily,  the  volitional 
stimulus  which,  causes  one  muscle  or  group  of  muscles 
to  contract  causes  also  the  opposing  muscle  or  group  to 
relax  ;  and  this  relaxation  permits  of  elongation  by  the 
contracting  opponent.  In  other  words,  the  pressure  within 
or  the  force  of  the  contracting  muscle,  is  greater  than  that 
of  the  relaxing  opponent.  But  if  we  suppose  that  as  the 
result  of  inflammation  of  anterior  horn  cells,  or  injury  of 
the  nerve  trunk,  a  muscle  is  incapable  of  carrying  out 
its  function,  combustion  is  interfered  with,  whereby  its 
pressure  is  lowered,  and  it  is  in  the  state  of  a  muscle  which 
has  relaxed  to  allow  its  opponent  to  act.  Equilibrium 
between  the  muscle  and  its  opponent  is  upset,  and  if  the 
normal  muscular  engine  is  not  prevented  it  will  be  found 
that  under  some  volitional  stress  it  will  pull  on  the  damaged 


PRINCIPLES  23 

engine  and  cause  its  elongation  ;  in  other  words,  the  normal 
muscle  will  physiologically  contract.  But  apart  from 
volition  this  physiological  contraction  need  not  necessarily 
occur. 

Thus,  if  we  had  a  paralysis  of  the  pronators  of  the 
forearm  from  division  of  the  median  nerve,  occurring  with 
the  hand  in  the  position  midway  between  pronation  and 
supination,  apart  from  volition,  aided  in  some  cases  by 
gravity,  there  is  no  reason  why  contracture  should  occur. 
There  is  no  immediate  rebound  of  the  normal  opponent 
producing  contracture.  But  perhaps  the  patient  brings 
the  hand  to  the  mouth,  and  supination  is  necessary.  The 
supinated  hand  cannot  be  pronated,  arid  unless  passively 
restored  to  its  old  position  it  remains  supinated.  But 
perhaps  for  a  fortnight,  or  longer,  the  supinators  are  not 
"  contracted  " — the  hand  can  readily  be  passively  restored. 
But  supposing  it  remained  supinated  for  six  weeks,  it  may 
then  be  difficult,  or  even  impossible,  in  spite  of  the 
patient's  volition  and  outside  passive  help,  to  pronate  the 
forearm — the  normal  and  physiologically  contracted  supi- 
nating  muscle  has  now  become  chronically  shortened.  But 
primarily  the  contracture  of  the  unopposed  muscle  or  group 
of  muscles  is  physiological ;  it  is  volitional.  If  in  the  above 
condition  the  pronators  at  the  end  of  a  week  completely 
recovered,  nothing  pathological  had  occurred  in  the  cells 
of  the  supinators  to  prevent  their  immediate  relaxation 
and  elongation  by  voluntary  pronation. 

Chronic  shortening  of  muscle  occurs  most  frequently 
in  the  flexors  of  the  knee  following  paralysis  of  the  quadri- 
ceps, in  the  pect oralis  major  following  paralysis  of  the 
deltoid,  and  in  the  extensors  of  the  ankle  (tendo  achillis) 
following  paralysis  of  the  flexors  of  the  ankle.  In  these 
instances  the  gravitational  effect  of  the  weight  of  the  leg, 
or  of  the  upper  limb  or  of  the  foot,  would  be  a  primary 
factor  in  producing  contraction,  in  addition  to  the  volitional 
contraction  of  the  normal  flexors,  adductor,  or  extensors. 
Why  the  physiological  contraction  has  become  chronic  is 
not  due  in  my  opinion  to  a  further  physiological  or  pathg- 


24  THE    ACTION    OF    MUSCLES 

logical  change  in  the  cells  of  the  muscle,  but  to  the 
correlated  shortening  of  the  fibro-elastic  elements.  These 
are  present  in  varying  degree  in  all  muscles,  and  include 
the  tendons  of  origin  and  insertion. 

The  chronically  shortened  or  contracted  muscle  is  the 
result  of  shortening  of  the  tendon,  and  of  the  fibrous 
elements  within  the  belly  with  which  the  tendons  are 
directly  continued.  It  is  an  adjustment  or  accommodation 
effect,  and  is  seen  in  connection  with  paralysis  of  the 
extensors  of  the  toes  and  of  the  tibialis  anticus,  where  the 
deep  fascia  of  the  front  of  the  leg  shortens  on  the  weakened 
irresistant  muscles.  Should  recovery  take  place  this  may 
actually  form  a  mechanical  barrier  to  muscular  action, 
unless  divided  or  even  partially  removed  by  the  surgeon. 
I  have  seen  these  muscles  bulge  out  nearly  half  an  inch 
when  the  deep  fascia  of  the  leg  has  been  divided.  This 
is  why  chronic  shortening  is  seen  especially  in  connection 
with  the  hamstrings  and  the  muscles  forming  the  tendo 
achillis.  In  the  case  of  the  deltoid  the  dragging  weight  of 
the  upper  limb — operating  whether  the  patient  is  erect  or 
lying  down — is  the  paramount  factor  in  producing  pectoral 
contraction.  It  is  interesting  to  note  that  in  a  young 
kangaroo  (saltatorial  marsupial)  the  total  length  of  the 
tendo  achillis  and  its  muscles  was  6J  inches — of  this  the 
tendinous  length  was  4  inches.  Unfortunately  shortening 
of  the  ligaments  of  a  joint  may  also  occur,  and  this  must 
be  remembered  in  connection  with  equinus  of  the  foot, 
where  the  posterior  ligament  of  the  ankle  may  be  so  shortened 
in  an  old  case  as  to  need  division.  If  we  take,  however, 
the  treatment  of  a  case  of  talipes  equinus  of  three  months' 
standing,  we  correct  the  foot  by  treating  the  tendon,  either 
dividing  it  or  lengthening  it  by  operation. 

Treatment  is  a  purely  mechanical  question.  Within  ten 
days,  when  the  lengthened  tendon  had  sufficiently  repaired, 
I  have  seen  the  tendo  achillis  muscles  contracting  normally, 
so  as  to  elongate  their  relaxed  opponents,  although  the 
former  muscles  had  been  chronically  contracted.  The 
state  of   "  chronic  contraction "   had   not  interfered  with 


PRINCIPLES  25 

the  effectiveness  of  the  muscle  cell.  From  the  physio- 
logical standpoint  it  was  normal,  only  the  muscle  was 
mechanically  prevented  from  being  elongated  either  pas- 
sively— even  under  an  anaesthetic — or  by  the  contraction, 
in  cases  of  "  paralysis/'  of  a  recovered  opponent,  although 
the  cell  itself  had  the  normal  power  of  relaxing  and  con- 
tracting. This  can  also  be  demonstrated  with  the  patient 
lying  down  in  the  case  of  a  pectoralis  major  which  is 
"contracted,"  when  the  muscle  will  only  allow  of  abduc- 
tion of  the  arm  to  60  degrees.  There  is  obviously  no 
interference  with  relaxation  of  the  pectoralis  muscle  cell, 
since  it  allows  the  deltoid  to  elongate  it  to  60  degrees  ; 
nor  is  there  interference  with  the  contraction  of  the  pector- 
alis cell,  since  it  can  bring  the  arm  slowly  and  methodically 
to  the  side  again.  Similarly,  with  a  case  of  contracted 
tendo  achillis  in  which,  though  the  foot  cannot  be  dorsi- 
flexed  to  the  right  angle,  the  muscles  of  the  tendo  achillis 
may  contract  to  extend  the  foot  5  degrees  further  and  relax 
to  allow  the  foot  to  be  flexed  these  5  degrees. 

Deformities  of  limbs  produced  by  chronically  contracted 
muscles  acting  against  weakened  opponents  should  never 
be  seen.  These  are  not  necessary  accompaniments  of  par- 
alysis, as  some  would  seem  to  imagine.  They  are  avoidable. 
It  should  be  impossible  to  see  anywhere  spastic  claw  hands, 
dropped  wrists,  dropped  feet,  or  contracted  knees  or 
shoulders.  Ankylosis  of  joints  due  to  severe  bony  injury 
may  be  seen,  but  deformities  due  to  muscle  weakness 
should  always  be  prevented.  In  cases  of  childien  treated 
privately  parental  neglect  in  the  application  of  splints  must 
be  borne  in  mind.  If  the  above  view  be  correct,  it  follows 
that  the  treatment  of  contracted  muscle,  should  it  have 
been  allowed  to  occur,  is  simple  and  dependent  on  mechanical 
means. 

To  sum  up  as  to  causation,  we  find  that  as  the  result  of 
volition  the  normal  muscle  is  contracted.  By  volition  it 
can  also  relax,  but  owing  to  the  paralysis  of  its  opponent 
no  elongation  follows.  It  remains  permanently  contracted 
owing  to  the  correlated  shortening  of  the  fibrous  elements 


26  THE    ACTION    OF   MUSCLES 

of  the  muscle,  which  then  prevent  muscular  elongation 
should  recovery  of  the  opponents  occur.  The  indication 
is  to  elongate  either  by  mechanical  or  surgical  means  the 
shortened  fibrous  elements,  and  this  treatment  is  invariably 
successful.  The  chronically  contracted  muscle  is  not 
favourable  to  the  recovery  of  the  affected  opponent,  whose 
fibrous  elements  are  thereby  chronically  stretched.  This 
state  of  chronic  elongation  is  one  of  irritability  to,  and  not 
of  rest  for,  the  affected  muscle  cell.  In  treatment,  then, 
the  principle  to  be  borne  in  mind  is,  that  if  a  muscle  be 
chronically  contracted  by  shortening  of  its  tendons  and 
other  fibrous  elements,  it  will  elongate  if  coaxed,  but  not  if 
forced,  and  if  the  pressure,  however  slight,  be  continuous. 
In  children  especially,  in  whom  contractures  are  most  fre- 
quently met  with,  conservation  rather  than  destruction 
should  be  our  aim — the  preservation  of  structures  round  a 
joint  rather  than  their  division. 

Before  division  or  lengthening  of  adductors,  or  ham- 
strings, or  pectoralis,  or  biceps,  a  recourse  should  be  had 
to  concentrated  energy,  not  so  much  forceful  as  continuous. 
"In  animals/'  wrote  Hunter,  "there  is  more  variety  of 
motion,  but  in  plants  more  real  power.  A  small  vine  can 
raise  a  column  of  fluid  five  times  higher  than  a  horse 
can  ;  for  the  same  energy  which  in  the  animal  world  is 
weakened  by  being  directed  to  many  objects,  is,  in  the 
vegetable  world,  strengthened  by  being  concentrated  on  a 
few."  Concentration  of  opposing  force  may  be  regarded  as 
a  first  principle  in  the  treatment  of  contractures.  Given  a 
pressure,  however  slight  but  continuous  and  concentrated, 
and  contractuures  even  of  the  extreme  and  apparently  hope- 
less type  will  be  found  to  yield,  without  the  aid  of  what 
should  always  be  the  last  and  not  the  first  resort — the 
knife.  And  provided  this  principle  be  borne  in  mind  it 
matters  little  by  what  means  it  is  carried  into  effect.  Thus  I 
have  known  a  badly  contracted  knee  of  some  years'  standing 
yield  to  the  pressure  continuously  applied  for  three  months 
of  a  bandage  and  a  wooden  back  splint  extending  from  the 
upper  third  of  the  thigh  to  the  lower  third  of  the  leg. 


PRINCIPLES  27 

The  breaking  down  of  muscle  contraction,  like  the 
"  smashing  up  "  of  joint  adhesions  at  one  sitting  under  an 
anaesthetic,  cannot  be  too  vigorously  condemned  as  being 
unscientific  and  charlatanic.  It  is  an  attempt  to  overcome 
in  twenty  minutes  a  state  that  has  taken  nature  perhaps 
years  to  effect.  By  such  a  procedure  permanent  injury  is 
usually  done  to  the  muscle.  It  has  to  be  borne  in  mind 
that  just  as  the  fibrous  elements  of  one  muscle  or  group  of 
muscles  are  shortened,  so  also  are  the  similar  elements  of 
the  opponents  elongated.  It  takes  time  for  these  elongated 
fibres  to  tighten.  The  elongation  of  the  fibres  of  the  con- 
tracted group  should  be  pari  passu  with  the  tightening  of 
those  of  the  elongated  opponent.  Then  if  the  affected  muscle 
has  recovered,  equilibrium  will  be  restored  between  the 
elastic  and  the  true  muscular  elements  of  the  opposing 
groups.  Until  recovery  takes  place  in  the  muscle  cell  of 
the  weakened  opponent  there  will  always  be  a  liability  to 
return  of  contraction,  unless  this  is  mechanically  prevented. 
In  the  case  of  the  foot  with  a  tightly  contracted  tendo 
achillis  of  old  standing,  it  is  usually  impossible  by  ordinary 
mechanical  force  to  overcome  the  deformity.  Elongation 
of  the  tendon  by  surgical  interference  becomes  necessary. 
It  may  be  mentioned  that  contraction  of  the  tendo  achillis 
could  be  prevented  and  more  frequently  overcome  in  its 
early  stage,  if  it  were  recognized  that  it  is  not  sufficient 
merely  to  maintain  a  foot  at  right  angles.  Plaster  of  Paris 
from  the  ball  of  the  toes  to  the  middle  of  the  leg  is  of  little 
use.  Extension  of  the  knee  is  essential,  as  the  plantaris 
and  gastrocnemius,  both  of  which  terminate  in  the  tendon, 
arise  above  that  articulation. 

Even  should  recovery  of  the  flexors  of  the  ankle  have 
taken  place,  it  will  be  necessary  to  keep  the  foot  at  rest  for 
some  time  after  operation  to  allow  the  elongated  fibrous 
elements  of  the  flexors  to  shorten.  In  other  words,  without 
support,  the  flexors,  though  recovered,  may  be  unable  for 
some  time  to  hold  the  foot  at  a  right  angle.  In  such  a  case 
the  patient  when  resting  should  have  the  foot  in  a  back 
splint  and  a  right-angled  foot-piece ;  and  when  walking  about 


28  THE    ACTION    OF    MUSCLES 

should  wear  an  extensor  band  passing  from  the  dorsum  oi 
the  boot  to  a  metal  wing  applied  at  the  middle  of  the  front 
of  the  leg.  Contractures  associated  with  replacement  of  the 
muscle  fibres  by  connective  tissue,  as  seen  in  "  ischaemic  " 
paralysis  following  tight  bandaging,  or  in  connection  with 
syphilitic  myositis  are  probably  the  most  difficult.  When 
fleshy  contracted  muscles  like  the  psoas,  pectoralis  major, 
or  adductores,  are  not  yielding  to  treatment — and  this  it 
may  be  stated  is  extremely  rare — the  presence  of  a  luetic 
fibrosis  might  naturally  be  suspected. 

XL   Testing  for  Muscle  Action 

It  cannot  be  too  strongly  insisted  upon  that  there  is 
only  one  true  test  for  muscular  action,  the  volitional  test 
scientifically  applied.  It  is  the  only  test  which  takes  into 
account  the  two  elements  of  muscular  action,  the  contraction 
of  one  muscle  and  the  relaxation  of  its  opponent.  By  the 
volitional  test  we  are  enabled  to  determine  the  minimum 
action  from  which  the  muscle  can  be  re-educated  up  to  the 
maximum.  For  the  accurate  application  of  this  test,  the 
ancestral  history  of  the  muscle  must  be  considered.  We 
must  have  a  knowledge  of  the  lines  along  which  it  acquired 
its  maximum  function,  as  in  the  case  of  the  deltoid  and  the 
quadriceps.  In  addition,  we  must  consider  the  effect  of 
gravity  ;  the  placing  of  the  origin  and  insertion  of  the  muscle 
as  nearly  as  possible  on  a  level,  as  in  the  case  of  the  brachialis ; 
the  avoidance  of  frictional  effects  by  directing  that  the 
limb  should  be  placed  on  a  sheet  of  smooth  cardboard  ;  the 
position  in  which  the  "  moment  of  force  "  of  the  muscle  is 
greatest,  as  in  the  case  of  the  flexor,  pronators,  or  supinators 
of  the  forearm  ;  also  the  position  in  which  leverage  can  be 
most  effective,  as  in  testing  for  finger  flexion,  by  asking  the 
patient  to  first  dorsi-flex  at  the  wrist  joint. 

There  should  be  complete  normal  range  of  movement  of 
the  components  of  a  joint  that  constitutes  the  fulcrum  for 
the  affected  muscle.  Should  the  contraction  of  an  antagon- 
istic muscle  have  been  allowed  to  occur  through  neglect, 


PRINCIPLES  29 

this  should  be  first  overcome,  as  often  a  muscle  condemned 
as  hopeless  is  really  a  recovered  one  mechanically  prevented 
from  acting.  Tests  that  do  not  consider  these  principles 
can  be  dismissed  as  worthless.  On  these  the  prognosis 
should  be  based,  and  the  opinion  be  expressed  as  to 
whether  operative  interference  in  a  case  of  suspected  nerve 
injury  is  necessary  or  not.  Ignorance  of  these  principles 
and  failure  to  recognize  the  importance  of  the  insertion  of 
a  muscle  as  an  indication  of  its  function,  are  at  the  root 
of  the  scepticism  with  which  the  demonstration  of  an  early 
recovery  of  muscle,  after  nerve-muscle  injury,  is  received. 
Results  actually  present  are  doubted,  because  they  do  not 
conform  to  traditional  text -book  opinion.  It  is  interesting 
for  the  physiologist  to  explain,  why  after  repair  of  a 
complete  division  of  the  median  and  of  the  ulnar  nerves  in 
the  arm,  when  the  muscles  supplied  by  these  two  nerves 
were  tested  on  the  above  lines,  function,  though  small,  was 
found  in  nine  weeks  to  be  present  in  every  muscle  supplied 
by  these  nerves.  And  why  also,  as  the  result  of  re-education, 
there  was  a  complete  recovery  in  that  period  of  the  flexors 
of  the  wrist  and  of  the  pronators  of  the  forearm.  We  can 
test  for  recovery  and  commence  to  re- educate  after  nerve 
division  as  soon  as  the  surgeon  is  satisfied  that  firm  union 
has  occurred.  Graduated  or  pari  passu  re-education  is  not 
a  source  of  irritation  to  a  repairing  nerve.  To  those  not 
previously  acquainted  with  these  methods  the  early  stage 
at  which  muscular  movement  will  be  noted  will  come  as  a 
revelation. 

A  few  instances  are  wTorthy  of  mention  as  to  the  method 
by  which  muscles  are  usually  tested  for  action,  and  the 
unscientific  grounds  on  which  they  have  been  condemned 
as  hopeless  because  they  have  apparently  failed  to  respond 
to  massage  and  electric  treatment.  In  the  case  of  the 
flexor  of  the  forearm  it  is  usual  for  the  patient  to  be  asked 
to  bring  the  hand  up  to  the  mouth  from  the  hanging  down 
position  of  the  arm,  or  to  do  the  maximum  work  for 
that  muscle  of  100  units.  Here  the  weakened  muscle  is 
asked  to  bend  the  forearm  with  the  hand  against  gravity, 


30  THE    ACTION    OF    MUSCLES 

with  its  line  of  action  lying  parallel  with  the  long  axis 
of  the  extremity,  and  its  "moment  of  force"  being  at  a 
minimum.  The  patient,  on  the  contrary,  should  be  lying 
down  on  a  firm  bed  or  table  with  the  limb  resting  on  a  firm 
pillow,  the  elbow  should  be  passively  bent  to  a  right  angle 
— the  position  in  which  the  "  moment  of  force  "  is  greatest 
— and  any  movement  should  take  place  on  a  sheet  of 
powdered  cardboard  to  eliminate  all  frictional  effect. 

In  a  case  of  deltoid  paralysis  the  patient  is  invariably 
asked  to  elevate  the  arm  from  the  side  when  sitting  or 
standing  erect.  Yet  a  patient  who  fails  in  this  maximum 
effort  may  readily,  when  lying  flat,  abduct  the  arm  to  a 
right  angle.  How  often  do  we  find  a  quadriceps  regarded 
as  "  paralysed,"  because  the  patient  is  unable  when  sitting 
to  lift  the  heel  off  the  ground  with  the  knee  extended  ! 
Yet  such  a  quadriceps,  if  tested  with  the  patient  lying 
on  a  firm  bed,  may  extend  an  acutely  flexed  knee.  The 
pronator  teres  should  not  be  tested  with  the  patient 
sitting  erect  or  standing.  He  should  be  lying  down  with 
the  arm  resting  on  a  pillow,  the  forearm  at  a  right  angle 
and  midway  between  pronation  and  supination.  To  test 
the  inverting  or  everting  power  of  the  tibialis  anticus  or 
peroneus  brevis,  and  the  inverting  or  everting  power  of 
the  tibialis  posticus  or  peroneus  longus,  the  foot  should  be 
dorsi-flexed  in  the  case  of  the  two  former  and  extended 
(plantar-flexed)  in  the  case  of  the  two  latter. 

XII.    Correlations 

At  the  foundation  of  all  study  on  function  lies  not  merely 
a  knowledge  of  structure  but,  what  is  more  important  still, 
a  knowledge  of  correlated  structure  ;  and  this  constitutes 
what  is  meant  by  applied  comparative  anatomy.  The  study 
of  structural  correlations  throws  numerous  hints,  not  merely 
on  normal,  but  also  on  so  called  abnormal  or  monstrous 
structures.  Changes  regarded  as  monstrous  in  us  may  be 
seen  in  other  animals  to  be  correlated  to  other  changes  ;  in 
other  words,  nature  has  in  different  members  of  the  mamma- 


PRINCIPLES  31 

Han  class  carried  certain  of  her  adaptive  trends  farther  than 
with  us,  giving  us  an  indication  of  the  intended  procedure 
in  man.  Thus  light  is  thrown  on  the  mode  of  disappear- 
ance of  the  fibula,  the  possible  significance  of  a  cervical  rib, 
mode  of  disappearance  of  the  vermiform  appendix,  signifi- 
cance of  the  large  gut  in  the  economy,  and  on  the  functional 
value  of  certain  muscles.  When  we  speak  of  "  highest  " 
and  "  lowest  "  amongst  the  mammalia  we  refer  really  to  the 
relative  development  of  the  new  brain.  The  comparison 
relates  to  cerebral  and  not  to  physical  development.  Thus, 
if  we  take  the  case  of  the  vermiform  appendix,  we  find 
that  in  the  wombat  (marsupialia)  this  structure  has  evolved 
farther  towards  complete  disappearance  than  in  man.  By 
a  study  of  the  abdominal  cavities  of  the  koala  and  phalanger 
light  is  thrown  on  the  vital  importance  or  otherwise  of  the 
adrenal  glands  and  on  their  mode  of  disappearance.  When 
we  hear  it  stated  that  the  large  gut  is  practically  a  useless 
structure,  and  that  the  ideal  gut  is  a  simple  tube,  it  is  as 
well  to  reflect  that,  in  a  member  of  the  marsupialia,  namely, 
the  Tasmanian  devil,  such  a  canal  has  been  evolved.  A  study 
of  correlations,  however,  shows  this  animal  to  be  the  most 
defective  muscular  type  of  its  order.  If  nature  produces — 
and  apparently  she  is  doing  it  frequently — a  new  rib  in  the 
neck,  the  question  pertinently  arises,  as  also  in  the  case  of  the 
disappearance,  partial  or  complete,  of  a  bone  usually  present, 
for  example  the  fibula,  is  this  disappearance  or  appearance 
utilitarian  and  in  response  to  a  need  ?  In  other  words,  are 
there  evidences  of  correlation  of  the  rib  with  associated 
structures  indicative  of  permanency  in  the  effort  ?  If  symp- 
toms present  themselves,  are  these  due  to  a  failure  in  the 
correlating  process  either  natural  or  mechanically  produced  ? 
This  must  be  the  test  applied  to  all  so  called  abnormalities. 
Nothing  in  itself  should  be  regarded  as  abnormal  or 
monstrous  ;  the  variation  may  be  a  useless  one,  never- 
theless it  is  a  response  to  an  effect  or  need.  The  removal 
of  the  rib  can  only  be  scientifically  justifiable  when  it  is 
proved  that  removal  is  the  factor  necessary  to  secure 
adequate  correlations  of  the  adjacent  structures.     The  fact 


32  THE    ACTION    OF    MUSCLES 

that  complete  correlation  could  occur  was  demonstrated 
in  Turner's  celebrated  dissection  of  a  cervical  rib  extending 
to  the  first  thoracic  costal  cartilage,  in  which  a  complete 
adjustment  of  parts  could  be  demonstrated.  Similarly 
there  is  abundant  evidence  that  the  human  fibula  is  under- 
going adaptive  changes.  In  man,  so  called  "  congenital 
fractures  "   are  met  with  in  this  bone,   or  even  its  com- 


Fig.  5.— The  leg  and  foot  of  kangaroo. 

plete  disappearance  with  loss  of  the  outer  toes.  Such 
cases  may  serve  as  an  indication  of  ultimate  adaptation, 
although  in  causing  a  congenital  absence  of  the  human 
fibula  to  occur,  nature  has  carried  the  progress  of  one  of  the 
consequences  of  the  erect  position  and  associated  gait 
beyond  that  of  the  other  consequences  with  which  it  should 
be  co-ordinate.  It  is  not  enough  to  say  that  the  fibula  is 
disappearing,  unless  one  finds  correlative  evidence  in  the  toes 


PRINCIPLES  33 

and  muscles  of  the  leg  and  foot.  The  leg  of  the  kangaroo, 
in  which  the  lower  half  of  the  fibula  does  not  exist  separately 
from  the  tibia  (fig.  5),  throws  important  light  on  the  natural 
mode  of  disappearance  of  the  fibula.  Here  muscle  correla- 
tions can  be  studied,  and  also  the  method  of  correction  of  the 


Fig.  6. — The  leg  and  foot  of  koala  (Phascolarctos  cm  ere  us). 

error.  In  the  koala  the  relatively  large  fibula  is  associated 
with  an  opposable  hallux  (fig.  6),  and  in  this  animal  and  in 
the  phalanger  there  exists  a  greater  freedom  of  movement 
between  the  tibia  and  fibula  than  in  others  of  the  marsupialia. 
This  approaches  in  some  degree  the  rotation  between  the 
radius  and  the  ulna 
3 


34  THE   ACTION    OF    MUSCLES 

On  similar  lines  one  is  able  to  determine  the  "  survival 
value  "  in  man  of  a  muscle  such  as  the  brachio-radialis 
(supinator  longus) .  From  the  variety  of  functions  ascribed 
to  this  muscle  one  infers  that  it  is  regarded  by  many  as 
almost  the  most  important  in  the  upper  extremity.  To  it 
are  ascribed  the  triple  powers  of  pronation,  of  supination, 
and  of  flexion  of  the  forearm.  Those  who  ascribe  the  power 
of  elbow  flexion  to  this  muscle  seem  to  forget  that  this  would 
involve  the  relaxation  of  the  antagonistic  and  powerful 
triceps,  which  is  only  associated  with  brachialis  contraction. 
This  muscle  (brachio-radialis)  is  an  accessory  supinator. 
Its  insertion  is  on  a  bone  whose  muscles  permit  of  rotatory 
movements  only,  and  not  the  forward  and  backward  move- 
ments of  flexion  and  extension.  Its  maximum  development 
is  reached  in  the  wombat,  which  is  the  most  powerful  mus- 
cular animal  amongst  the  marsupials.  In  this  animal  it 
extends  above  as  high  as  the  spine  of  the  scapula,  and  has 
a  broad  attachment  below.  The  wombat  is  a  burrowing 
animal,  and  for  this  powerful  pronation  and  supination  are 
necessary  ;  the  hand  has  an  unopposable  polleX.  In  the 
koala  this  muscle  is  also  well  defined,  and  at  its  termination 
it  is  seen  to  cross  dorsal  to  the  radio-carpal  articulation  to 
terminate  at  the  lateral  side  of  the  carpus.  Its  development 
in  this  tree-climbing  marsupial  is  associated  with  a  double 
pollex  by  which  limb  grasping  is  improved.  In  man  the 
supinator  longus  has  a  narrow  tendinous  insertion  on  the 
lower  end  of  the  radius,  and  in  the  kangaroo  there  is  little 
muscular  belly,  the  greater  part  of  the  muscle  being  a  slender 
tendon  which  is  attached  more  proximal  and  more  exten- 
sively to  the  radius  than  in  man.  This  muscle  in  the  human 
upper  limb  can  be  regarded  not  as  one  possessing  a  multi- 
plicity of  function,  but  as  one  struggling  hard  to  retain  its 
place  in  the  human  economy. 

Muscle  Development  and  the  Thymus  Gland. — The 
thymus  gland  is  a  characteristic  of  early  human  life  ;  it 
commences  to  disappear  about  the  fifth  year,  and  in  the 
adult  nothing  is  to  be  seen  macroscopically.  At  birth  it 
weighs  |  oz.  or  more.     At  twenty-one  it  is  usually  a  remnant 


PRINCIPLES  35 

weighing  only  forty  grains,  and  after  twenty-five  it  is 
extremely  difficult  to  discover  any  of  its  structure  in  the 
mediastinal  tissues.  Cases  of  a  defined  human  thymus 
being  retained  throughout  life  are  recorded,  a  fact  of  no 
little  importance.  The  thymus  gland  is  at  its  maximum 
development  when  muscular  action  and  co-ordination  asso- 
ciated with  the  erect  posture  are  developing  ;  these  being 
well  established  it  commences  to  disappear.  In  the  recorded 
instances  of  its  persistence  throughout  life  its  presence  has 
presumably  been  a  necessity,  and  harmless.  Although  it 
commences  to  disappear  early,  the  question  arises,  should  it 
necessarily  disappear  then  ?  Is  its  absence  beneficial  in  all 
or  only  in  some  ?  Are  conditions  superimposed  causing  its 
too  early  disappearance  in  some  to  whom  perhaps  a  thymic 
secretion  may  be  a  necessity  ?  On  these  questions  a  study 
of  muscular  and  thymic  correlations  throws  some  interesting 
light. 

In  the  platypus  at  one  end  of  the  mammalian  scale,  in 
which  piscatorial,  avian,  and  mammalian  features  indicative 
of  instability  are  to  be  found,  the  thymus,  apart  from  any 
question  of  hibernation,  is  present  throughout  life.  I  have 
found  it  covering  the  ventral  and  lateral  surfaces  of  the  peri- 
cardium with  a  thickness  of  nearly  1/8  inch.  In  the  Tas- 
manian  devil  (Dasyurus  sarcophilus)  also,  a  well  developed 
thymus  is  retained  throughout  life.  This  exclusively  carni- 
vorous marsupial  has  during  the  past  century  offered  a  poor 
resistance  to  man,  and  like  the  Tasmanian  wolf  (Thylacinus) 
is  now  almost  extinct.  The  dasyures  or  carnivorous  marsu- 
pials represent  from  the  point  of  view  of  musculature  the 
poorest  developed  type  amongst  marsupials.  There  would 
appear  to  be  a  definite  relationship  between  this  and  the 
retained  thymus.  If,  on  the  other  hand,  we  were  asked  to 
designate  the  perfected  physical  type  from  the  point  of  view 
of  musculature  amongst  marsupials,  one  would  unhesitat- 
ingly refer  to  the  wombat.  Unprotected  by  law,  it  has  easily 
offered  the  greatest  resistance  to  the  presence  of  man  on  the 
Australian  continent.  Yet  in  this  animal  I  have  never  met 
with  the  presence  of  thymic  tissue  either  in  the  young  or  in 


36  THE    ACTION    OF   MUSCLES 

the  adult.  I  have  directed  attention  to  this  question  as 
possibly  throwing  light,  not  so  much  on  the  treatment  as 
on  the  causation  of  certain  muscular  and  nerve  diseases.  I 
would  suggest  the  use  of  thymus  gland  in  the  early  stages 
of  poliontyelitis  during  re-education,  and  similarly  during 
the  re-education  of  weakened  muscle  from  nerve  or  other 
injury.  The  question  is  suggested  whether  in  some  remote 
way  this  gland  is  associated  with  the  failure  in  man  of  a 
limb  to  regenerate  after  amputation — a  power  which  our 
remote  ancestors  before  the  evolution  of  the  mammalian 
type  appear  to  have  possessed  in  conjunction  with  a  highly 
developed  reflex  system. 

XIII.  Contraction,  Relaxation,  and  Elongation  of 
Muscle  :  Elasticity 
When  we  use  the  term  "  muscular  action  "  we  are  not 
referring  to  the  single  action  of  muscular  contraction,  but 
to  a  double  physiological  action,  namely  contraction  and 
shortening  of  the  muscle  producing  the  desired  effect  at  the 
fulcrum  or  centre  of  motion,  since  the  origin  and  insertion 
are  approximated  ;  and  relaxation  and  elongation  of  its 
opponent.  The  voluntary  stimulus  causing  one  muscle  or 
set  of  muscles  to  contract  causes  also  relaxation  of  the 
opposing  muscle  or  set  of  muscles.  Just  as  important  as 
a  knowledge  of  the  action  of  a  muscle  is  a  knowledge  of  the 
action  of  its  opponent.  A  muscle  fibre  cannot  be  in  a  state 
of  physiological  relaxation  and  physiological  contraction 
at  one  and  the  same  time.  Contraction  and  relaxation  of 
muscle  are  two  opposite  physiological  states.  Relaxation 
does  not  mean,  as  some  have  supposed,  a  cessation  in 
function  of  the  muscle  fibre.  It  is  as  much  a  physiological 
action  as  contraction  ;  and  it  is  to  be  remembered  that 
muscles  which  contract  at  death  do  not  relax  post-mortem. 
Normally,  muscles  in  life  maintain  a  constant  action  which 
is  known  as  "  tone,"  but  neither  contraction  nor  relaxation 
of  muscles  is  produced  after  death.  In  a  normal  muscle 
during  life  there  is  no  such  thing  as  a  state  of  absolute  rest 
or  inaction,  so  that  in  connection  with  fixation  of  muscle, 


PRINCIPLES 


37 


for  example  in  bone  or  joint  injury  or  disease,  we  can 
never  produce  absolute  rest  of  normal  muscle.  This  can 
only  be  produced  by  death.  Elongation  of  muscle,  on  the 
other  hand,  is  not  a  physiological  action,  but  is  produced 
as  the  result  of  a  mechanical  action.  Whether  we  are 
dealing  with  voluntary  or  involuntary  muscle,  elongation 


Fig.  7. — Diagrammatic  representation  of  muscular  action, 
and  reciprocal  elongation. 

depends  for  its  production  on  some  outside  force.      The 
power  of  elongation  is  not  inherent  in  the  muscle  fibre. 

Relaxation  is  essential  for  elongation,  it  must  precede  it ; 
but  there  is  no  inherent  force  in  a  relaxed  fibre  that  pro- 
duces elongation.  In  the  case  of  voluntary  muscle  the 
relaxed  muscle  (R)  is  elongated,  owing  to  the  contraction 
and  shortening  of  its  opponent   (S).      When  the  relaxed 


38  THE    ACTION    OF    MUSCLES 

muscle  fibre  (R)  in  its  turn  contracts,  the  opponent  (S) 
simultaneously  relaxes,  and  is  itself  in  turn  elongated  (fig.  7). 
Thus  the  opposing  muscles  or  groups  of  muscles  throughout 
the  body  become  in  turn  reciprocal  elongators  of  each  other. 
In  the  case  of  involuntary  muscle  action,  as  in  the  pro- 
pulsion of  food  along  the  gastro-intestine,  elongation  is  pro- 
duced by  the  mechanical  impaction  of  food.  The  presence 
of  food  in  a  suitable  state  of  digestion  is  the  stimulus  to 
contraction  of  that  portion  of  the  gastro-intestine  with  which 
it  is  in  contact — the  successive  portion  of  intestine  becomes 
relaxed  to  allow  of  the  propulsion  of  food  by  which  it  is 
elongated,  and  this  portion  in  its  turn  contracts,  propelling 
the  food  into  the  adjacent  distal  relaxed  portion. 

The  action  of  an  elastic  body  is,  on  the  other  hand,  of  an 
essentially  different  nature  from  that  of  a  muscular  one. 
An  elastic  body  can  produce  movement  by  shortening,  after 
it  has  been  stretched,  just  as  muscle  can  ;  but  two  opposing 
pieces  of  elastic  tissue,  unlike  two  opposing  pieces  of  mus- 
cular tissue,  cannot  reciprocally  elongate  each  other.  The 
muscle  fibre  has  the  power  in  itself  of  producing  motion  ; 
it  can  relax  and  contract.  An  elastic  fibre  has  no  inherent 
power  of  contraction  or  relaxation,  and  it  is  dependent  on 
an  outside  power  which  is  not  elastic  for  its  elongation.  By 
this  elongation  it  is  enabled  to  produce  motion  on  a  part, 
since  it  is  always  striving  to  arrive  at  the  normal  state  in 
which  it  is  not  stretched,  and  this  it  does  as  soon  as  the 
stretching  force  is  removed.  Unlike  muscular  action  the 
property  of  elasticity  is  not  affected  by  death.  We  can 
inject  and  dilate  blood  vessels  after  death,  or  stretch  a 
tendon  which  shortens  when  the  stretching  force  is  removed. 
By  means  of  their  elastic  property  the  ligaments  of  a  joint 
are  enabled  to  accommodate  themselves  to  alterations  in 
the  angles  of  the  components  of  the  articulation,  which 
alterations  cannot  be  produced  by  ligaments,  but  by  muscle. 
The  ligaments,  when  stretched,  are  factors  which  are  always 
endeavouring  to  approximate  the  angle  of  the  components 
of  a  joint  to  the  normal.  The  use  of  elastic  substance  in 
muscle  is  in  connection  with  the  state  of  equilibrium  between 


PRINCIPLES  39 

two  opposing  muscles  or  opposing  groups  of  muscles.  The 
elastic  components  would  be  constantly  striving  to  produce 
the  state  of  equilibrium,  and  indeed  this  may  also  be  said 
of  the  muscle  fibres.  When  a  contracted  muscle  (S)  (fig.  7) 
relaxes,  its  elongation  towards  the  middle  state  of  equilibrium 
is  the  result  as  much  of  the  recoil  of  the  elastic  substance 
of  the  contracting  muscle  (R)  as  of  the  action  of  the  contract- 
ing muscle  itself  (R)  which  had  been  elongated.  Beyond 
that,  action  would  appear  to  be  solely  muscular.  The  state 
of  equilibrium  is  the  state  when  muscles  or  groups  of  muscles 
are  equally  balanced,  not  only  as  regards  pressure  or  tension 
in  the  muscle  fibres,  but  also  when  the  opposing  elastic  fibres 
are  themselves  in  a  state  of  equilibrium.  When  two  opposing 
muscles  or  opposing  groups  of  muscles  are  paralysed,  the 
position  of  rest  corresponds  to  the  normal  position  of  equili- 
brium between  the  two  groups.  A  muscle  which  is  elongated 
during  normal  muscular  action  presents  a  firm,  tightened  feel 
to  the  touch,  which  is  often  and  erroneously  regarded  as  a 
state  of  contraction.  Thus,  when  we  stand  erect,  although 
the  hamstrings  feel  firm,  they  are  in  a  state  of  relaxation  and 
elongation  owing  to  the  contraction  of  the  quadriceps  by 
which  the  erect  position  is  maintained.  If  we  bend  the  body 
back  at  the  knee,  the  flexors  of  the  knee  contract  and  the 
quadriceps  relaxes  and  elongates,  but  this  latter  is  pari  passu 
with  the  contraction  of  the  hamstrings.  In  other  words, 
flexion  is  not  an  unregulated  action  of  the  flexors  ;  by  means 
of  the  extensors  a  too  forcible  action  of  the  benders  is  pre- 
vented. Relaxation  of  muscle  is  thus  essentially  an  active, 
not  a  passive  state  ;  the  relaxation  of  the  opponent  goes 
hand  in  hand  with  the  action  of  the  contracting  muscle.  A 
good  example  of  the  evil  attendant  on  the  uneven  balance 
between  elongation  and  contraction  of  opponents  is  seen  when 
a  person  in  danger  of  falling  backwards  makes  a  sudden  mus- 
cular effort  to  prevent  this.  This  effort  causes  a  spasmodic 
contraction  of  the  quadriceps  without  pari  passu  relaxation 
and  elongation  of  the  flexors,  and  may  result  in  a  yielding 
either  of  the  patella  itself  or  of  the  ligamentum  patella. 
When  I  use  the  term  "centre  of  motion  or  fulcrum  "  in 


40  THE    ACTION    OF    MUSCLES 

reference  to  the  action  of  muscles  or  groups  of  muscles  I  do 
not  refer  to  the  centre  of  motion  of  the  body,  which  would 
appear  to  be  at  the  hip  j  oints  ;  but  to  the  particular  j  oint,  the 
angles  of  whose  components  are  altered  by  the  muscle  or 
muscles  when  they  produce  motion.  When  I  use  the 
term  "  muscular  opponents  of  a  joint  "  I  refer  to  muscles 
or  groups  of  muscles  which  have  the  power  of  reciprocally 
contracting  and  elongating  about  the  same  centre  of  motion, 
and  not  to  muscles  which  are  merely  passing  over  the  par- 
ticular centre  of  motion  to  act  on  some  distant  articulation. 
Thus,  if  we  take  the  case  of  weakened  flexor  action  of  the 
second  and  third  phalanges  of  the  fingers  (sublimis  and 
profundus),  we  find  that  the  patient  will  invariably  dorsi- 
flex  the  wrist  to  obtain  the  benefit  of  good  leverage.  This 
he  does  by  contracting  one  and  reciprocally  relaxing  the 
other  of  the  two  opposing  groups  of  muscles  acting  on  the 
same  centre  of  motion  at  the  wrist  joint. 

The  stimulus  to  contraction  of  the  extensores  radialis 
longus  and  brevis  and  the  carpi  ulnaris  calls  into  physio- 
logical relaxation  the  flexores  carpi  radialis  and  ulnaris, 
by  means  of  which  the  contracting  extensors  are  enabled 
mechanically  to  elongate  them.  With  this  motion  the 
muscles  acting  on  the  fingers  have  absolutely  no  connection. 
We  can  produce  this  position  of  the  wrist  with  the  fingers 
either  flexed  or  extended,  abducted  or  adducted.  The  long 
flexors  of  the  fingers,  though  passing  over  the  wrist,  do 
not  act  on  it  :  their  contraction  does  not  call  into  relaxa- 
tion the  extensors  of  the  wrist  without  which  flexion  of 
the  wrist  is  not  possible.  Their  action  calls  into  relaxation 
the  extensors  of  the  two  distal  inter-phalangeal  articula- 
tions on  which  they  act,  namely  the  interossei.  Similarly, 
the  extensor  communis  which  produces  extension  at  the 
metacarpo-phalangeal  joints  of  the  fingers  does  not  extend 
the  wrist.  The  same  stimulus  that  produces  its  contrac- 
tion does  not  cause  relaxation  of  the  flexors  of  the  wrist 
without  which  extension  is  impossible.  On  the  contrary,  it 
produces  relaxation  of  the  muscles  which  act  on  the  same 
joints,   those  which  have  the   same  centre   of  motion   or 


PRINCIPLES  41 

fulcrum,  namely  the  lumbricales,  and  which  are  the  benders 
of  the  metacarpophalangeal  joints  of  the  fingers. 

In  the  case  of  the  elbow  the  muscles  which  have  the 
same  centre  of  motion,  the  humero-ulnar  joint,  are  the 
brachialis  in  front  and  the  triceps  behind.  The  stimulus 
necessary  to  produce  contraction  in  the  one  simultaneously 
produces  relaxation  in  the  other.  By  means  of  these 
muscles,  and  these  only,  flexion  and  extension  of  the  elbow 
joint  are  produced.  The  biceps  brachii  is  a  supinator. 
The  stimulus  that  produces  its  contraction  causes  pronator 
relaxation,  without  which  its  action  is  impossible.  Its 
centre  of  motion  is  radio-ulnar  and  not  humero-ulnar. 
This  stimulus  does  not  produce  relaxation  also  of  the 
powerful  triceps,  without  which  elbow  flexion  is  impossible. 
The  brachialis  is  the  only  muscle  whose  stimulus  to  con- 
traction has  that  effect.  The  supinator  longus  (brachio- 
radialis)  is  often  erroneously  described  as  a  flexor  of  the 
elbow.  It  has  no  such  power.  It  is  attached  to  the 
radius,  which  has  a  rotatory  motion  (pronation  and  supi- 
nation). The  centre  of  motion  for  the  action  of  the  long 
supinator  is  radio-ulnar,  and  the  stimulus  for  its  contraction 
does  not  simultaneously  call  into  relaxation  the  powerful 
extending  triceps  without  which  elbow  flexion  is  impossible. 
It  may  be  argued  that  if  a  movable  elbow  joint  be  impro- 
vised with  the  bones  of  the  upper  limb,  and  if  straps  be 
attached  corresponding  to  the  insertion  of  the  biceps  or 
supinator  longus,  traction  on  these  straps  will  produce 
flexion  of  the  elbow  joint,  and  hence  these  muscles  must 
be  elbow  flexors.  That  argument  holds  if  the  question  of 
triceps  action  be  excluded.  It  will  not  hold  if,  for  example, 
a  splint  be  fixed  dorsal  to  the  elbow  joint  so  as  to  prevent 
its  motion,  for  that  is  practically  what  the  contracted 
triceps  corresponds  to  as  regards  the  supinator  longus 
and  biceps  in  a  normal  upper  extremity. 

XIV.    Reverse  Action 
In  "  reverse  action  "  there  is  an  alteration  of  the  terms 
applied  to  the  termination  of  the  muscles.     What  is  usually 


42  THE   ACTION    OF   MUSCLES 

regarded  as  the  origin  of  the  muscle  becomes  the  insertion, 
and  what  is  usually  regarded  as  the  insertion  becomes  the 
origin.  Thus  in  the  case  of  the  brachialis  the  insertion  into 
the  ulna  becomes  the  origin,  and  its  attachment  to  the 
humerus  or  origin  becomes  the  insertion.  The  reverse 
action  is  seen  when  we  flex  the  body  on  the  fixed  forearm 
and  hand,  as  in  elevating  the  body  from  the  ground  on  the 
horizontal  bar  (fig.  26).  Here  we  are  dealing  with  a  joint 
(humero-ulnar)  admitting  of  flexion  and  extension  only,  and 
acted  on  by  muscles  (brachialis  and  triceps)  which  pass  over 
it  only.  So  that  whether  we  are  bending  or  extending  with 
either  muscular  extremity — the  arm  or  the  forearm — as  the 
origin  or  insertion  the  physiological  action  is  the  same.  The 
contraction  of  one  muscle  causes  relaxation  of  its  opponent 
acting  on  the  same  centre  of  motion.  In  the  case  of  reverse 
action  of  a  muscle  passing  over  two  joints,  as  for  example  the 
sartorius  or  the  gastrocnemius,  it  is  the  knee  joint  in  the  one 
case  and  the  ankle  in  the  other  which  constitute  the  centre 
of  motion  respectively  for  these  muscles,  whether  the  action 
be  what  is  called  "  normal  "  or  "  reverse/'  Thus  it  is 
usually  stated  that  the  gastrocnemius  with  its  fixed  point 
below  acts  as  a  flexor  of  the  femur  on  the  tibia  ;  this  implies 
that  contraction  of  the  gastrocnemius  can  call  into  physio- 
logical relaxation  the  extensor  of  the  knee  joint,  the  quadri- 
ceps. That  muscle  is  antagonized  however  by  the  muscles 
which  have  the  same  centre  of  motion  or  fulcrum,  namely 
the  flexors  of  the  knee.  They  alone  can  call  the  quadriceps 
into  a  physiological  state  of  relaxation.  The  muscles  acting 
on  the  ankle,  and  having  the  same  centre  of  motion  as  the 
gastrocnemius,  are  the  flexors  of  the  ankle.  It  is  their 
relaxation  which  permits  of  the  action  of  the  gastrocnemius, 
and  the  result  of  the  reversed  action  of  the  gastrocnemius 
and  the  soleus  is  a  limited  extension  backward  of  the  whole 
body  at  the  ankle  joint. 

Taking  its  fixed  point  from  below,  the  sartorius  is  described 
as  a  flexor  of  the  pelvis  on  the  thigh.  The  centre  of  motion 
for  the  sartorius  is  the  knee  joint.  If  the  knee  be  fixed  in 
the  extended  position,  as  when  we  stand,  it  seems  to  be 


PRINCIPLES  43 

forgotten  that  the  quadriceps  extensor  has  contracted  to 
produce  this  because  all  the  flexors  of  the  knee  including 
the  sartorius  are  relaxed  and  elongated.  Furthermore,  con- 
traction of  the  sartorius  does  not  call  into  physiological 
relaxation  the  extensor  of  the  hip  joint,  the  gluteus  maximus, 
without  which  flexion  of  the  pelvis  on  the  femur  at  the  hip 
joint  is  impossible.  The  gluteus  maximus  has  its  own  re- 
ciprocal elongator,  the  ilio-psoas  or  flexor  of  the  hip,  and 
contraction  of  the  ilio-psoas  alone  is  accompanied  by 
physiological  relaxation  of  the  gluteus  maximus. 

XV.  Muscles  passing  over  Several  Joints 
Muscles  passing  over  several  joints,  as  the  biceps  (shoulder, 
elbow,  and  radio-ulnar)  or  the  long  flexors  and  extensors  of 
the  fingers,  are  with  their  opponents  in  a  state  of  equilibrium 
as  regards  all  the  movements  of  the  joints  over  which  they 
pass.  They  are  only  concerned  with  their  own  particular 
function,  and  in  the  case  of  the  flexor  profundus  digitorum 
this  is  an  action  on  the  last  phalanx  of  the  fingers  resulting 
in  an  alteration  of  the  relations  of  the  components  of  the 
distal interphalangeal  joints.  The  profundus  is  not  a  flexor 
of  the  elbow,  wrist,  or  metacarpophalangeal  joints.  We 
can  flex  the  distal  phalanx  of  the  fingers  in  the  position 
either  of  flexion  or  extension  of  these  joints. 

The  power  that  muscles  have  of  adapting  themselves  to 
alterations  which  take  place  in  the  natural  distance  between 
their  origin  and  insertion,  as  a  result  of  action  on  the  joints 
over  which  they  pass  by  the  particular  muscles  of  those 
joints,  would  appear  to  depend  on  their  elastic  components. 
Thus  when  we  flex  the  second  and  third  phalanges  o.f  the 
fingers  with  a  flexed  wrist,  and  then  extend  the  wrist  still 
keeping  our  phalanges  bent,  this  does  not  mean  an  alteration 
in  the  physiological  state  of  the  muscle  fibre  or  cell  of  the 
profundus  and  sublimis,  which  remains  one  of  contraction. 
The  centres  of  motion  for  these  muscles  are  the  inter- 
phalangeal articulations,  and  only  actual  alterations  of  the 
angle  of  the  centre  of  motion  would  be  associated  with  alter- 
ation of  the  physiological  state  of  the  muscle  cell.     Again,  if 


44  THE    ACTION    OF    MUSCLES 

with  the  forearm  at  a  right  angle  to  the  arm  we  over-supinate, 
this  is  due  to  the  action  of  the  biceps  assisted  by  the  supina- 
tors, and  also  to  accompanying  relaxation  of  the  pronatores. 
If  we  further  flex  the  elbow,  which  is  due  to  brachialis  con- 
traction and  triceps  relaxation,  some  slight  shortening  of 
the  biceps  will  be  noted  ;  this  is  due  to  the  elastic  com- 
ponents of  the  biceps  accommodating  themselves  to  the 
altered  angle  of  the  elbow  joint.  It  is  not  due  to  a  phy- 
siological contraction  of  the  biceps  acting  as  a  bender  of 
the  elbow  as  is  erroneously  described,  since,  with  the  elbow 
joint  flexed  from  a  right  angle  to  45  degrees  by  the  brachialis, 
we  can  relax  the  biceps  by  over-pronation  of  the  forearm. 

XVI.    Specialization  of  Muscle  Function 

Each  muscle  can  be  regarded  as  a  specialist  as  regards 
function,  and  should  several  functions  be  ascribed  to  a 
muscle  these  can  only  be  regarded  as  the  result  of  one  con- 
traction. A  muscle  cannot  be  at  one  time  an  extensor  and 
at  another  a  flexor  as  is  described  in  the  case  of  the  inter- 
ossei  of  the  hand.  These  muscles  are  supposed  by  some  to 
have  the  dual  power  of  flexing  the  metacarpo-phalangeal 
joints  and  of  extending  the  interphalangeal  ones.  This 
however  is  not  so,  since,  if  we  flex  the  two  interphalangeal 
joints,  which  we  do  by  contracting  the  profundus  and  sub- 
limis,  the  interossei,  as  the  extensors  of  these  joints,  must 
be  in  a  physiological  state  of  relaxation.  Yet  holding  the 
interphalangeal  joints  flexed  we  can  flex  also  at  the  meta- 
carpo-phalangeal joints.  This  we  do  by  contraction  of  the 
lumbricales  and  relaxation  of  the  extensor  communis. 

Under  normal  conditions  of  volitional  control,  the  two 
states  of  contraction  and  relaxation  cannot  be  considered 
as  existing  in  the  one  muscle  at  the  same  time.  In  spasm, 
which  is  abnormal,  an  irregular  action  of  muscle  fibres  may 
occur.  Similarly  a  portion  of  a  muscle  may  be  artificially 
stimulated,  or  the  normal  action  may  be  interfered  with 
owing  to  trauma  of  portion  of  the  nerve  supply  or  portion 
of  the  muscle.     Speaking  generally  however,  when  the  whole 


PRINCIPLES  45 

muscle  acts  it  produces  one  general  effect,  having  one  de- 
fined action  ;  and  its  combined  force  acts  in  the  line  of  the 
resultant  of  the  forces  exerted  by  its  component  fibres.  This 
combined  action  is  only  possible  on  account  of  the  nervous 
mechanism  by  which  the  numerous  fibrils  composing  the 
muscle  are  connected.  The  deltoid  muscle,  though  it  has  an 
extensive  origin,  has  a  comparatively  narrow  insertion — the 
fibres  converge  towards  a  narrow  area  to  produce  a  com- 
bined action.  We  see  it  stated  that  "  the  anterior  fibres  of 
the  deltoid  assisted  by  the  pectoralis  major  draw  the  arm 
forwards,  and  the  posterior  assisted  by  the  teres  major 
and  latissimus  dorsi  draw  it  backwards."  This  means 
physiologically  that  if  the  anterior  fibres  draw  the  humerus 
forwards  they  are  contracted  and  shortened,  and  the  pos- 
terior fibres  which  draw  the  humerus  backwards  are  in  this 
movement  relaxed  and  elongated,  two  opposite  physiological 
states  existing  in  a  muscle  at  one  and  the  same  time.  This 
statement  of  deltoid  action  is  erroneous,  and  leads,  in  a' 
student's  mind,  to  endless  confusion.  The  insertion  of  the 
deltoid  is  our  guide  for  function.  It  should  be  regarded 
simply  as  an  abductor  of  the  arm  and  its  physiological 
opponent  is  the  pectoralis  major. 

XVII.    Synergists 

In  any  muscular  action  throughout  the  body  there  are 
numerous  other  muscles  at  work — synergists — whose  action 
though  secondary  is  designed  to  help  the  principal  move- 
ment. Thus  in  lifting  a  weight  above  the  head  not  only 
the  muscles  of  the  upper  extremity  are  at  work,  but  the 
muscles  of  the  trunk  and  of  the  lower  limbs,  which  maintain 
the  erect  position,  an  essential  for  this  action,  also  participate. 
In  picking  up  an  object  from  the  table  when  sitting,  it  is  not 
only  the  opposed  action  of  the  thumb  to  the  fingers  ;  but 
the  forearm,  elbow,  and  shoulder  muscles  are  also  brought 
into  action.  The  essential  action  however  is  the  opposition 
of  thumb  to  the  fingers,  and  although  we  make  a  routine  of 
certain  combinations,  these  do  not  warrant  the  stress  that 
has  been  laid  upon  them.    Thus  we  can  pick  an  object  off 


46  THE    ACTION    OF    MUSCLES 

the  table  with  the  wrist  or  elbow  flexed  or  extended,  and 
the  arm  abducted  or  adducted  at  the  shoulder.  We  can 
abduct  the  little  finger  with  the  wrist  abducted  or  ad- 
ducted, flexed  or  extended,  or  midway  between  flexion  and. 
extension. 

What  the  student  should  particularly  remember  is  that 
the  components  of  combined  muscular  movements  are 
muscles  or  groups  of  muscles  in  a  state  of  either  relaxation 
and  elongation,  or  contraction  and  shortening,  and  acting 
at  different  but  specific  centres  of  motion.  Thus  in  abduc- 
tion of  the  little  finger  with  the  elbow  flexed  and  the  wrist 
dorsi-flexed  we  have  at  the  elbow  contraction  of  the  bra- 
chialis  and  relaxation  of  the  triceps  ;  at  the  wrist  relaxation 
of  the  wrist  flexors  and  contraction  of  the  wrist  extensors. 
The  essential  movement  of  abduction  of  the  little  finger 
due  to  contraction  of  the  abductor  minimi  digiti  is  possible 
owing  to  adductor  relaxation,  and  to  that  only.  This 
action  takes  place  at  the  metacarpophalangeal  joint  of  the 
little  finger,  which  is  the  centre  of  motion  or  fulcrum,  and 
is  independent  of  the  action  of  muscles  which  have  not  that 
articulation  as  their  fulcrum  or  centre  of  motion. 

XVIII.    Mechanism  of  Muscular  Contraction 

As  to  the  nature  of  the  mechanism  of  muscular  action 
whether  it  can  be  explained  by  physical  or  chemical  methods, 
we  must  still  confess  our  ignorance.  But  the  ignorance  of 
cause  does  not  prevent  us  from  investigating  the  principles 
by  which  muscular  action  is  regulated,  or  from  studying  the 
effects  of  action.  Charles  Bell  regarded  muscle  contractibility 
as  an  original  endowment  of  nature,  imparted  in  a  way  that 
could  not  be  known.  Older  anatomists  regarded  the  muscle 
fibre  as  a  hollow  tube  from  end  to  end  ;  or  a  chain  of  cells 
of  various  shapes,  some  rhomboidal,  some  circular,  some 
cylindrical,  which  contained  foreign  matter  capable  of  being 
acted  on.  Following  Newton's  great  discoveries  the  nerves 
and  muscles  were  regarded  by  others  as  containing  "  the 
rare  elastic  spirit  "  which  he  concluded  to  be  diffused 
throughout  the  universe.    The  effect  of  mental  effort  was  to 


PRINCIPLES  47 

communicate  a  pulsation  to  this  elastic  spirit  in  the  nerve, 
and  so  to  the  same  spirit  within  the  juices  wherewith  the 
muscle  cells  were  rilled,  and  the  result  was  a  rarefication  and 
dilatation  of  the  juices.  When  the  mind  ceased  to  act  the 
impulses 'propagated  in  the  elastic  spirit  ceased,  and  the 
muscular  fluid,  whose  expansion  was  occasioned  by  these 
pulsations,  subsided,  and  so  relaxation  was  accounted  for. 

In  recent  times  perhaps  the  most  important  view  put 
forward  is  that  of  Professor  MacDougall,  "  that  osmosis 
might  occur  between  the  interior  of  the  fibril  and  the  sarco- 
plasm  outside."  It  seems  certain  that  with  contraction  of 
a  muscle  lactic  acid  is  evolved,  and  the  contracted  muscle 
as  compared  with  its  relaxed  and  elongated  opponent  is  in 
a  state  of  increased  tension.  Oxidation  is  the  accompani- 
ment of  relaxation  or  lowered  tension,  not  of  contraction  or 
increased  tension,  and  with  relaxation  of  fibre  lactic  acid  is 
absent.  To  resort  to  a  mechanical  simile  muscle  fibres 
always  have  steam  up.  They  are  always  ready  for  action, 
and  as  stated  a  muscle  can  only  be  completely  rested  when 
this  "  irritability  "  "  tone  "  or  "  inherent  power  "  has  gone, 
i.e.  post-mortem.  This  power  on  the  part  of  the  muscle  fibre 
of  keeping  up  steam  or  tension  corresponds  to  the  power  of 
the  hepatic  cells  to  secrete  bile,  or  the  pancreatic  cells  to 
secrete  pancreatic  juice.  Its  function  has  disappeared  when 
it  loses  that  power,  just  as  the  function  of  the  pancreatic  cell 
has  gone  when  it  is  unable  to  secrete  pancreatic  juice.  As 
an  engine  with  a  pressure  of  80  lbs.  will  move  an  engine 
pulling  in  the  opposite  direction  with  a  pressure  of  40  lbs., 
so  will  the  contracting  muscle  whose  pressure  is  greater,  pull 
and  elongate  the  opposing  or  relaxed  muscle  whose  pressure 
is  less.  In  the  state  of  equilibrium  between  two  physiologi- 
cally opposing  muscles  or  groups  of  muscles  the  tension  or 
pressure  in  the  opposing  muscle  fibres  is  of  equal  intensity. 
Under  similar  conditions  the  two  engines,  each  with  40  lbs. 
pressure,  are  unable  to  affect  one  another.  What  corresponds 
in  the  muscle  fibre  to  steam  in  the  engine  is  still  unsolved. 
The  explanation  of  this  problem  might  almost  be  regarded 
as  the  explanation  of  life  itself,  for  after  all  life  is  motion. 


CHAPTER    II 
THE    SHOULDER    REGION 

The  upper  limb  of  man  with  its  fine  intrinsic  and  extrinsic 
adjustments  can,  in  comparison  with  the  lower  limb,  be 
regarded  as  correlated  to  intellectuality.  The  main  function 
of  the  lower  limb  is  support,  and  its  principal  movements 
are  the  forward  and  backward  ones  of  flexion  and  extension. 
It  is  more  important  to  prevent  ankylosis  in  the  upper  than 
in  the  lower  extremity,  since  in  spite  of  fixation  of  the  three 
main  lower  limb  joints  a  patient  may  walk  comparatively 
well.  In  man  so  fine  are  the  muscle  adjustments  in  the  upper 
limb  that  the  loss  of  function,  for  example,  of  the  adductor 
or  opponens  pollicis  interferes  at  once  with  the  opposition 
of  thumb  to  fingers,  an  essential  movement  for  grasping. 
Of  the  pronator  teres,  in  which  case  food  when  placed  in 
the  hand  can  be  conveyed  to  the  mouth,  but  owing  to  the 
fixed  Oversupinated  position  of  the  hand  cannot  originally 
be  grasped.  Of  the  supinators,  in  which  example  food  can 
be  grasped,  but  owing  to  the  hand  being  fixed  in  the  position 
of  overpronation  cannot  be  conveyed  to  the  mouth.  The 
loss  of  any  of  these  functions  may  be  sufficient  to  ruin  for 
practical  purposes  the  utility  of  the  limb — a  condition  of 
affairs  that  would  never  occur  in  the  case  of  the  lower 
extremity. 

It  is  interesting  to  note  that  poliomyelitis  affects  the 
upper  limb  much  less  frequently  than  the  lower,  and  adult 
affection  of  the  former  is  extremely  rare.  If  cases  of  upper 
limb  paralysis  from  this  disease  are  treated  early  and 
effectively  on  lines  which  recognize  the  ancestral  sequence 
of  acquisition  of  function,  recovery  is  much  more  rapid 
and  complete  in  the  upper  than  in  the  lower  limb — a  result 


THE    SHOULDER    REGION 


49 


quite  opposed  to  former  statistics.  Nor  is  the  reason  hard 
to  seek.  More  perfect  rest  is  secured,  volitional  control  of 
muscular  action  is  better,  and  the  easier  working  from  the 
"  zero  "  position  renders  the  muscles  of  the  forearm  and 
hand  more  responsive  than  those  of  the  leg  and  foot.  It 
might  at  first  appear  somewhat  strange  to  state  that  there 
could  possibly  be  any  association  between  two  marsupial 


Fig.  8.— Quadriceps  extensor  paralysis  (case  of  infantile  paralysis). 

animals — the  wombat  and  koala— representing  life  on  this 
planet  many  ages  ago,  and  a  soldier  from  the  recent  French 
battlefields  who  has  been  wounded  in  the  shoulder  region 
with  resulting  inability  to  raise  his  arm  above  his  head. 
In  this  connection  it  is  first  necessary  to  define  particularly 
two  very  important  characteristics  of  man's  erect  or  ortho- 
grade posture. 

(i)  That  the  quadriceps  muscle  produces  the  essential 

4 


50 


THE    ACTION    OF    MUSCLES 


stiffening  of  the  knee  which  enables  the  erect  standing 
attitude  to  be  maintained  ;  failure  to  effect  this  is  the  cause 
of  the  swinging  limb  and  crutchdom  met  with  so  often  in 
old  untreated  cases  of  infantile  paralysis  (fig.  8). 

(2)  That  not  only  has  the  upper  limb  been  dispensed  with 


Fig.  9. — The  deltoid  region  of  koala. 

D,  Deltoid  ;   P,  Pectoralis  major  ;   H,  Biceps  ;  B,  Brachio-radialis  ;   R,  Triceps  ; 
T',  Deltoid;   T,  Trapezius. 


as  a  means  of  bodily  support  in  progression,  but,  although 
dependent,  it  can  be  raised  above  the  head. 

These  are  the  latest  muscular  functions  to  be  acquired 
by  man,  for  even  such  closely  related  mammals  as  the  orang 
and  chimpanzee  walk  with  the  aid  of  the  fore  limb,  and  the 


Fig.  io. — Muscles  of  the  fore  limb  of  the  wombat  (Phascolomys  Mitchelli). 

T,  Trapezius ;  P,  Pectoralis  major  ;  B,  Biceps  ;  AT,  Triceps;  F,  Digital  and  hand  flexors; 
E,  Extensors ;  R,  Brachio-radialis ;  S,  Sterno  mastoid ;  H,  Trachea. 


5o] 


THE    SHOULDER    REGION  51 

knee    slightly    bent.      Yet    nature    experimented    in    this 
direction   when   the   marsupial  was   the   highest   form   of 
mammalian  life  on  the  earth.     The  selective  factor  was  in 
all  probability  drought.     It  drove  the  wombat  below  the 
surface  of  the  ground  for  water  and  roots.     It  drove  the 
koala  to  the  trees  for  the  eucalyptus  leaf.     Incidentally  a 
vermiform  appendix  developed  in  the  former,  and  a  caecum 
sometimes  8  ft.  long  in  the  latter.     In  the  case  of  the  koala 
(fig.  9)  the  ability  to  raise  the  arm  was  not  associated  with 
orthograde  posture.    The  erect  posture  and  the  ability  to 
raise  the  hand  above  the  head  were  not  correlated  in  the 
marsupials.     There  was  a  partial  success  in  the  kangaroo. 
The  perfected  correlation  in  man  occurred  many  years  later. 
In  effecting  elevation  of  the  hand  from  the  hanging  position 
to  above  the  head,  nature  was  not  prodigal  in  muscle  ex- 
penditure.    The  keynote  to  the  movement  of  elevation  of 
the  upper  extremity  is  to  be  found  in  the  characteristic 
development  of  the  deltoid  muscle  as  seen  in  man — deltoid 
development   at   the  expense   of  trapezius  and  pectoralis 
major.     The  trapezius  instead  of  extending  to  the  humerus 
with  the  pectoralis,  as  is  seen  in  the  wombat,  became  limited 
by  the  spine  of  the  scapula,  the  acromion  process,  and  the 
clavicle  (fig.  10) .     For  the  study  of  this  important  evolution 
the  koala  and  kangaroo  (marsupialia)  afford  abundant  evi- 
dence.    The  action  of  the  supraspinatus  as  an  abductor  of 
the  arm  is  subsidiary  to  that  of  the  deltoid,  and  would  ap- 
pear to  be  associated  with  external  rotation  of  the  humerus. 
It  is  important  to  notice  that  its  development,  unlike  that 
of  the  deltoid,  is  not  associated  with  the  acquisition  of  the 
power  of  elevation  of  the  fore  limb.     In  an  animal  like  the 
wombat  in  which  there  is  neither  attempt  at  the  erect 
posture  nor  elevation  of  the  fore  limb  the  supraspinatus  is 
a  well-developed  muscle.      The  deltoid  in  man  is  a  lever 
of  the  third  degree,  the  power  is  between  the  weight  to  be 
raised  and  the  fulcrum  or  centre  of  motion  at  the  shoulder 
joint.      This   ensures   velocity.     As   evidence   of   strength, 
though  it  has  an  extensive  origin  it  is  concentrated  at  its 
insertion  into  the  middle  of  the  outer  surface  of  the  shaft 


52  THE    ACTION    OF    MUSCLES 

of  the  humerus  which  is  at  some  distance  from  the  centre  of 
motion.  It  is  a  fleshy  muscle,  the  fibres  being  strengthened 
by  fibrous  septa  to  improve  attachment.  The  arrangement 
of  the  anterior  and  posterior  fibres  is  linear  and  that,  of 
the  central  ones  bipennate.  Once  able  to  maintain  the 
abducted  arm  in  relation  to  the  acromion  by  means  of  the 
deltoid  assisted  by  the  supraspinatus,  nature  found  that 
all  that  was  necessary  for  further  elevation  was  a  rotatory 
movement  of  the  scapula.  No  new  muscles  were  called  into 
being.  She  utilized  the  rhomboids,  trapezius,  serratus,  and 
levator  anguli  scapulae  by  giving  them  new  rotatory  func- 
tions ;  and  as  the  abduction  and  rotatory  powers  are  recent 
so  also  are  they  unstable,  easily  lost,  and  regained  in  cases 
of  injury  or  disease  with  difficulty. 

MUSCLES    OF   THE    SHOULDER    REGION    IN    MAN 

It  is  necessary  to  distinguish  between  two  groups,  viz.  : 
(i)  Muscles   arising   chiefly   from   the   scapula   to   move 

the  humerus  ; 
(2)  Muscles   inserted   into   the   scapula   to   produce   the 

movements  peculiar  to  that  bone. 

1.  Muscles  moving  the  Humerus 

All  these  with  the  exception  of  the  pect oralis  major  and 
latissimus  dorsi  arise  from  the  scapula. 
They  are  : 

Abductors. — Deltoid  and  supraspinatus. 
Adductor. — Pectoralis  major. 

External  rotators. — Infraspinatus  and  teres  minor. 
Internal  rotators. — Latissimus  dorsi  and  subscapularis. 
Flexor. — Coraco-brachialis. 
Extensor. — Teres  major. 
Deltoid. — This  thick  fleshy  triangular  muscle  which  gives 
the  rounded  form  to  the  shoulder  arises  from  the  outer  third 
of  the  clavicle,  outer  border  of  the  acromion  and  the  lower 
margin  of  the  spine  of  the  scapula.     The  fibres  converge 


THE    SHOULDER    REGION 


53 


from  this  extensive  origin  to  a  narrow  tendinous  insertion 
at  the  middle  of  the  outer  side  of  the  humerus.  Though 
limb  muscles  usually  have  their  insertion  nearer  to  the 


INFRA  S  PIN  A  TUS 


PINATUS  u      SUPRASPINATUS 
(Ext:  rotater)  i     ^^(  Abductor) 


SUBSCAPULAR 
(inc.-  rotater) 

LATISSIMUS 
,  DORS)  . 

[int.  rotater) 


TERES  MAJ&J 
(Extender) 


BRACHIAUIS 

(Bender) 


BRACHIAUIS 
ANT. 


Anconeus 
Fig.   ii. — The  insertions  of  muscles  moving  the  humerus. 

centre  of  motion  than  the  origin,  yet  in  the  case  of  the 
deltoid  and  coraco-brachialis  the  origin  is  nearer  the  centre 
of  motion  than  the  insertion.     The  effect  however  is  the 


54  THE   ACTION    OF   MUSCLES 

same  in  each,  action  being  produced  with  a  minimum  con- 
traction. The  insertion  of  the  deltoid  into  the  humerus 
corresponds  to  a  triangular  area  about  2  J  inches  long  with 
a  greatest  width  of  about  1  inch.  The  width  of  its  origin 
is  about  7  inches.  Thus  a  muscle  whose  width  of  origin  is 
7  inches  operates  on  an  area  whose  width  is  only  1  inch. 

Supraspinatus. — This  is  so  called  because  it  arises  from 
the  hollow  on  the  back  of  the  scapula  above  the  spine. 
It  becomes  adherent  to  the  shoulder  capsule,  and  is  inserted 
into  the  highest  facet  of  the  great  tuberosity  of  the  humerus. 
By  its  attachment  to  the  capsule  of  the  shoulder  joint,  this, 
though  lax,  is  prevented  from  being  impacted  between  the 
humerus  and  glenoid  cavity  when  the  arm  is  raised  above 
the  head. 

Pectoralis  Major. — This  arises  from  the  front  oftheinner 
half  of  the  clavicle,  from  half  of  the  front  of  the  sternum  and 
costal  cartilages  as  low  as  the  seventh  cartilage,  and  by  a 
slip  from  the  aponeurosis  of  the  external  oblique  of  the 
abdomen.  The  fibres  converge  towards  the  upper  arm,  and 
the  muscle  twisting  on  itself  is  inserted  by  a  flat  tendon 
about  if  inches  wide  into  the  outer  or  lateral  margin  of  the 
groove  in  the  upper  third  of  the  humerus  for  the  passage  of 
the  biceps  tendon. 

Infraspinatus. — This  thick  and  fleshy  muscle  arises  from 
the  infra-spinous  fossa  on  the  back  of  the  scapula  and  is 
inserted  into  the  capsule  of  the  joint  like  the  supraspinatus, 
and  also  into  the  middle  facet  of  the  great  tuberosity  of 
the  humerus. 

Teres  Minor. — This  like  the  teres  major  is  so  called  from 
its  apparent  roundness  when  first  dissected.  It  arises  from 
the  lower  or  axillary  margin  of  the  scapula  and  is  inserted 
into  the  lowest  of  the  three  facets  on  the  great  tuberosity 
of  the  humerus,  and  into  the  bone  immediately  below  it. 
It  is  worth  remembering  that  the  strong  fibro-muscular 
attachment  of  the  infraspinatus  and  teres  minor  measures 
about  2  inches  in  width. 

Latissimus  Dorsi. — This  broad  flat  muscle  arises  in  the 
loins,  being  attached  to  the  spines  of  the  six  lower  thoracic, 


THE    SHOULDER    REGION  55 

lumbar,  and  sacral  vertebraae,  also  from  the  back  of  the  crest 
of  the  ilium  and  by  fleshy  digitations  from  the  dorsal  portions 
of  the  four  lower  ribs.  It  is  traced  up  and  out  round  the 
side  of  the  trunk,  the  fibres  converging  on  the  dorsum  of  the 
spine  of  the  scapula  into  a  thick  fasciculus  which  twisting 
on  itself  is  finally  inserted  by  a  flat  riband-like  tendon  on 
the  bottom  and  inner  edge  of  the  bicipital  groove  opposite 
that  of  the  pectoralis  major.  One  is  struck  by  the  rela- 
tively weak  insertion  for  such  an  extensive  muscle  which  is 
less  pronounced  than  the  much  smaller  muscle — the  teres 
major. 

Subscapularis. — This  is  a  fleshy,  strong,  somewhat  fan- 
shaped  muscle,  lining  like  a  cushion  the  ventral  surface  of 
the  scapula  from  which  it  arises.  Its  fibres  are  inserted 
by  a  broad  thick  tendon  into  the  lesser  tuberosity  of  the 
humerus,  and  into  the  neck  and  shaft  of  the  bone  below  the 
tuberosity  for  about  1  inch.  This  muscle  at  its  insertion 
measures  about  if  inches  in  width. 

Coraco-Brachialis. — This  narrow  but  fleshymuscle  arises 
from  the  apex  of  the  coracoid  process  and  is  inserted  at  the 
middle  of  the  inner  surface  of  the  shaft  of  the  humerus. 
This  muscle  is  fleshy  almost  to  its  insertion,  which  is 
equal  in  length  to,  but  slightly  narrower  than,  the  teres 
major. 

Teres  Major. — This  arises  from  the  dorsal  aspect  of  the 
lower  angle  of  the  scapula  and  is  inserted  by  a  flat  tendon 
into  the  inner  or  medial  margin  of  the  bicipital  groove  close 
to  that  of  the  latissimus  dorsi.  If  we  examine  a  humerus 
specially  prepared  to  show  the  insertion  of  muscles  we  find 
that  the  tendon  of  the  teres  major  lies,  at  its  insertion,  not 
merely  medial  but  distinctly  dorsal  to  that  of  the  latissimus 
dorsi.  The  insertion  of  the  teres  major  is  seen  when  the 
bone  is  viewed  from  the  dorsal  aspect.  This  has  an  important 
bearing  on  the  function  of  the  teres  major.  Though  this 
muscle  is  usually  described  as  an  internal  rotator,  it  is 
important  to  remember  that  we  can  flex  or  extend  the 
humerus  in  the  position  of  external  or  internal  rotation  at 
the  shoulder  joint. 


56  THE    ACTION    OF    MUSCLES 

(2)  Muscles  which  act  on  the  Scapula 

These  are  : 

Trapezius. — This  rotates  the  scapula  upwards,  back- 
wards towards  the  spine,  and  outwards  (elevation)  from 
the  chest  wall,  rotating  also  the  clavicle  upwards  and  back- 
wards. It  is  assisted  by  a  direct  elevator  acting  at  the 
superior  angle,  the  levator  scapulae,  which  arises  from  the 
transverse  processes  of  the  upper  four  cervical  vertebrae, 
and  is  inserted  into  the  vertebral  border  of  the  scapula 
from  the  superior  angle  of  the  spine  on  the  dorsal  aspect. 

Serratus  Magnus  or  Anterior. — Its  action  is  to  draw  the 
scapula  inwards  to  the  chest  wall,  downwards,  and  forwards. 
It  is  the  antagonist  of  the  trapezius,  and  is  assisted  by  the 
subclavius,  which  passing  from  the  first  rib  near  its  cartilage 
to  the  under  surface  of  the  middle  third  of  the  clavicle  draws 
the  clavicle  downwards  and  forwards. 

Rhomboids. — Draw  the  scapula  backwards  towards  the 
spine  and  somewhat  upwards. 

Pectoralis  Minor. — The  antagonist  of  the  rhomboids 
draws  the  scapula  forwards  and  somewhat  downwards. 

Trapezius. — This  muscle  receives  its  name  owing  to  its 
lozenge  form  and  to  older  anatomists  was  known  as  the 
cucularis  from  its  resemblance  to  the  monk's  cowl.  This 
fleshy  muscle  arises  above  from  the  skull,  being  attached  to 
the  external  protuberance  of  the  occipital  bone  and  the 
adjacent  superior  curved  line ;  from  the  ligamentum 
nuchae  which  extends  from  the  protuberance  to  the  seventh 
cervical  spine,  and  from  the  spines  of  all  the  thoracic  verte- 
brae. The  upper  fibres  pass  down  and  out  to  be  inserted 
into  the  outer  third  of  the  clavicle,  the  intermediate  fibres 
pass  out  to  the  acromion  and  upper  border  of  the  spine  of 
the  scapula,  and  the  lower  fibres  pass  up  and  out  and  form 
a  flat  tendon  which  is  inserted  into  the  root  of  the  spine  of 
the  scapula. 

Serratus  Magnus  or  Anterior. — This  fleshy  muscle  lies 
upon  the  side  of  the  chest  extending  between  the  ribs  and 
the  scapula.      It  arises  by  a  series  of  fleshy  tongues  or 


THE    SHOULDER    REGION  57 

digitations  from  the  lateral  aspect  of  the  upper  eight  ribs. 
Its  insertion  is  into  the  whole  length  of  the  vertebral  border 
of  the  scapula  on  its  ventral  or  anterior  aspect. 

Rhomboids  (major  and  minor). — The  origin  is  from 
the  lower  part  of  the  ligamentum  nuchae  and  the  spines  and 
supraspinous  ligaments  of  seventh  cervical  and  upper  five 
thoracic  vertebrae.  The  insertion  is  into  the  vertebral 
border  of  the  scapula  on  its  dorsal  aspect  extending  from 
the  spine  of  the  scapula,  to  the  inferior  angle. 

Pectoralis  Minor. — This  triangular  muscle  lies  beneath 
the  pectoralis  major.  It  arises  by  three  digitations  from 
the  third,  fourth,  and  fifth  ribs  near  their  cartilages,  and 
is  inserted  by  a  flat  tendon  into  the  coracoid  process  of 
the  scapula. 

Elevation  of  the  Upper  Limb 
When  we  speak  of  paralysis  of  the  shoulder  or  scapular 
region,  we  invariably  refer  to  the  inability  either  to  raise 
the  arm  to  a  right  angle,  or  the  arm  and  hand  above  the 
head.  The  exact  mechanism  by  which  we  raise  the  hand 
above  the  head  has  been  the  subject  of  discussion  for  many 
years.  In  the  first  place  it  may  be  observed  that  the  upper 
extremity  is  connected  with  the  trunk  only  at  one  relatively 
small  point,  the  sterno-clavicular  articulation.  At  the  outer 
end  of  the  clavicle,  where  it  is  related  to  the  acromion, 
strengthening  the  acromio-clavicular  capsule,  we  have  the 
firm  coraco-clavicular  ligaments,  the  conoid  and  trapezoid. 
Here  there  is  little  movement  of  the  scapula  on  the  clavicle, 
and  Bell  regarded  this  as  almost  a  fixed  point.  The  deltoid 
assisted  by  the  supraspinatus  abducts  the  arm  to  a  right 
angle.  Farther  movement  of  the  humerus  upwards  is  pre- 
vented by  the  acromion  projecting  over  it.  This  farther 
movement  is  not  performed  at  the  shoulder  or  gleno-humeral 
joint,  but  is  rendered  possible  by  a  rotatory  movement  of 
the  scapula  and  the  clavicle  on  the  trunk. 

The  principal  motion  takes  place  at  the  sterno-clavicular 
articulation,  and  the  clavicle  has  been  well  described  as 
a  shaft  or  axis  on  which  the  scapula  rotates  together  with 


58  THE   ACTION    OF   MUSCLES 

the  humerus,  which  is  fixed  to  it  by  the  deltoid  and  supra- 
spinatus.  As  the  scapula  does  not  appear  to  rotate 
through  an  angle  of  90  degrees  in  this  movement,  Cath- 
cart  held  the  view  that  the  final  part  of  the  movement  in 
this  second  arc  took  place  in  the  shoulder  joint.  The 
principal  motor  machine  in  this  second  movement  is  the 
trapezius  which  has  been  described  as  a  continuation  of 
the  deltoid,  both  being  attached  to  the  outer  third  of 
clavicle,  acromion,  and  spine  of  the  scapula.  The  trapezius 
in  this  motion  is  assisted  by  the  levator  scapulae  and  the 
rhomboids.  By  means  of  the  serratus  magnus  passing  from 
the  ribs  to  the  ventral  surface  of  the  vertebral  border  of 
the  scapula,  the  latter  maintains  its  relation  with  the  chest 
wall.  This  is  a  position  necessary  for  scapula  rotation  and  for 
depression  of  the  limb  after  elevation — in  this  latter  action 
the  serratus  is  assisted  by  the  subclavius.  Where  this  is 
interfered  with  as  in  serratus  paralysis  the  scapula  is  elevated 
from  the  chest  wall  and  raised  upwards,  giving  rise  to  the 
characteristic  winging  of  the  scapula  ;  and  then  elevation  of 
the  hand  above  the  head  is  not  possible  (see  figs.  12-17). 
In  paralysis  of  the  deltoid,  trapezius,  or  serratus,  the  reason 
why  the  patient  consults  us  is  the  inability  to  raise  the 
hand  from  the  side  above  the  head. 

Positions  of  Anatomical  Rest  for  Loss  of  Muscular 
Power  in  the  Shoulder  Region 

Trapezius. — In  a  case  of  loss  of  muscular  power  in  the 
trapezius  muscle,  which  is  not  so  common  as  that  of  the 
deltoid,  the  arm  should  be  abducted  to  an  angle  of  not  less 
than  145  degrees.  This  can  be  easily  effected  by  means  of 
an  upper  limb  abduction  splint  the  stem  of  which  is  tilted 
up  at  the  axilla.  While  the  splint  is  being  made,  to  effect 
this  the  sleeve  can  be  immediately  pinned  to  a  pillow,  and 
another  pillow  placed  in  the  axilla  with  the  patient  in  bed. 
I  prefer  the  metal  splint  to  any  plaster  appliances,  a  great 
advantage  being  that  it  can  be  removed  in  a  few  seconds 
for  the  purpose  of  muscle  re-education. 


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en 
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Fig.  i 6. — The  inability  when  erect  to  elevate  the  upper  limbs  beyond 
the  right  angle. 


Fig.  17. — Method  of  re-education. 


5&] 


THE    SHOULDER    REGION  59 

Deltoid. — Here  a  similar  procedure  is  adopted,  the  stem 
of  the  abduction  splint  being  placed  at  a  right  angle — and 
the  scapula  rotated  backwards.  In  this  way  the  contrac- 
tion of  the  antagonist  pectoralis  is  best  prevented.  The 
following  is  the  model  of  the  splint  (fig.  18)  first  introduced 
by  me  at  the  Australian  Medical  Congress,  October  1908, 
and  exhibited  at  Bologna,  Italy,  in  1909. 

The  basis  is  a  stem  of  malleable  iron  \  inch  wide  and  \  inch 
thick.  This  runs  up  the  mid-axillary  line  from  about  1  inch 
above  the  costal  edge  to  the  axilla  and  follows  the  required 
contour  of  the  under  surface  of  the  arm  and  forearm  to  the 

SHOULDER    BANDS 
AXfLLA 


CHEST    W//VGS 


Fig.   18. — The  upper  limb  abduction  splint. 

wrist,  being  bent  to  the  requisite  angle  at  the  axilla  and 
elbow.  At  the  latter,  flexion  almost  to  a  right  angle  will  be 
found  most  suitable  for  the  patient.  A  piece  of  aluminium 
or  tin  shaped  to  the  hand  is  attached  at  the  wrist  termination 
so  as  to  allow  the  mid  prone  and  supine  position,  and  the 
fingers  rest  on  a  pad  of  wool.  Wings  J  inch  by  TV  inch  are 
attached  at  the  wrist,  elbow,  and  upper  arm,  and  two  wings 
pass  round  the  chest  being  attached  to  the  stem,  one  at  the 
costal  extremity  and  the  other  below  the  apex  of  the  axilla. 
The  ends  of  these  chest  wings  are  connected  anteriorly  by 
strap  and  buckle.  The  limb  is  lightly  bandaged  on,  and 
pieces  of  webbing  crosswise  over  each  shoulder  from  the 
back  to  the  front  are  sufficient  to  hold  the  splint  well  into 
the  armpit. 

Serratus. — The  hand  of  the  affected  side  is  placed  on  the 


60  THE    ACTION    OF    MUSCLES 

opposite  shoulder  with  the  elbow  at  the  side  and  maintained 
in  this  position  by  means  of  a  bandage  sling  round  the  neck 
(see  figs.  14  and  15).  In  this  position  all  winging  of  the 
scapula  disappears,  the  scapula  is  brought  downwards,  for- 
wards, and  inwards  to  the  chest  wall,  while  the  opponents  of 
the  serratus  are  relaxed  and  elongated.  There  is  little  doubt 
that  in  cases  of  loss  of  power  about  the  shoulder  rest  in  bed 
at  the  time  of  injury  or  after  nerve  operation  should  be  in- 
sisted on  as  much  as  possible.  In  an  early  infantile  paralysis 
case,  this  should  be  the  rule  until  recovery. 

Method  of  Re-education  for  Muscular  Weakness  in 
the  Shoulder  Region 

A  paralysed  limb  should  at  all  times  be  handled  with  the 
greatest  gentleness.  The  muscular  engine  will  not  respond 
to  force,  but  will  respond  to  gentle  coaxing.  When  taken 
off  the  splint  with  the  patient  lying  down  the  limb  should 
occupy  at  first  the  position  it  had  when  supported  by  the 
splint.  The  arm  with  a  paralysed  deltoid  should  not  be 
allowed  to  drop  when  the  splint  is  removed.  We  should  be 
as  careful  to  avoid  unnecessary  movement  as  in  the  case  of 
a  fracture  of  the  humerus.  Hence  also  the  importance  of 
a  firm  bed,  so  that  movements  can  be  carried  out  without 
unduly  disturbing  the  patient.  At  first  it  is  best  to  place  a 
sheet  of  powdered  cardboard  under  the  limb  to  obviate  all 
resistances  to  movement.  In  re-education  to  enable  the 
patient  to  raise  the  hand  from  the  side  to  above  the  head 
three  separate  arcs  of  a  circle  must  be  carefully  borne  in 
mind.  These  patients  invariably  have  the  volitional  test 
applied  when  standing  or  sitting  erect.  But  of  one  thing 
we  can  be  certain,  if  the  patient  cannot  elevate  the  arm  when 
lying  flat  on  the  back  either  on  a  table  or  firm  bed,  he  will 
not  be  able  to  accomplish  this  when  erect.-  It  is  impossible 
to  perform  100  units  of  work  if  the  muscles  fail  at  10.  We 
give  the  minimum  test  for  recovery  by  commencing  work 
with  the  patient  lying  flat  and  with  a  folded  sheet  under  the 
head.     We  commence  at  "  zero  "  (A  B,  fig.  19),  the  patient 


THE    SHOULDER    REGION 


61 


being  gradually  elevated  by  means  of  pillows  placed  under 
the  head  and  shoulders  along  the  planes  E  B,  C  B,  and  H  B, 
till  the  sitting  erect  plane  D  B  is  reached.     Apart  from  this 


arc,  which  refers  to  the  position  of  the  body  relative  to  the 
limb,  we  have  for  consideration  the  fact  that  deltoid  abduc- 
tion and  scapula  rotation  also  represent  two  distinct  arcs. 


Fig.  20. 


In  order  to  re-educate  weak  muscles  of  the  shoulder 
region  these  two  separate  arcs  of  deltoid  abduction,  H  B 
(fig.  20)  and  of  scapula   rotation  B  D  (fig.  20),  must  be 


62  THE    ACTION    OF    MUSCLES 

considered  in  every  case.  Work  should  begin  in  the 
absolutely  horizontal  plane  A  B  (fig.  19),  full  movement 
obtained  in  that,  and  then  gradually  increased  to  the  full 
vertical  plane  D  B  (fig.  19)  in  the  manner  described.  Full 
movement  in  both  arcs  of  deltoid  abduction  and  of  scapula 
rotation  must  be  obtained  in  any  one  of  the  body  planes 
E  B,  C  B,  H  B  (fig.  19)  before  proceeding  to  the  next 
highest — this  next  one  is  then  reached  as  stated  by  gradual 
elevation  of  the  patient. 

In  fig.  20  the  line  A  B  represents  the  arm  held  abducted 
to  a  right  angle.  It  represents  the  maximum  work,  or 
100  units,  for  the  deltoid  in  whatever  plane  of  the  body  we 
are  working.  But  the  completion  of  the  arc  H  B  does  not 
necessarily  mean  that  we  can  enter  the  arc  B  D  (scapula 
rotation).  In  commencing  work  in  the  arc  B  D  at  A  B 
we  are  asking  the  muscles  that  produce  rotation  of  the 
scapula  to  perform  their  work  at  the  maximum  disadvantage. 
With  the  arm  hanging  at  the  side,  represented  by  the  line 
A  H,  we  have  the  humerus  in  the  position  where  to  raise 
it  the  deltoid  is  asked  to  do  a  maximum  of  work.  But  the 
weakened  deltoid  is  incapable  of  doing  that  work,  and  in 
that  position  is  at  its  maximum  disadvantage.  Further- 
more, it  is  in  that  position  overstretched  by  a  dependent 
limb  to  its  greatest  extent.  It  cannot  pull  right  up  the 
hill.  We  place  the^limb  at  a  right  angle,  keep  it  supported 
there,  and  are  certain  we  can  lower  it  and  go  from  C  to  B 
before  we  attempt  H  to  B.  In  this  way  we  have  a  certain 
means  of  testing  recovery  and  of  regulating  the  amount  of 
muscular  work.  We  have  not  only  to  coax  our  muscle 
to  functionize  with  the  limb  in  the  easiest  position,  but 
similarly  with  the  position  of  the  limb  relative  to  the  rest 
of  the  body. 

Deltoid  Re-education. — With  the  patient  lying  on  his 
back  on  a  firm  bed  or  table  and  with  a  slight  support  under 
the  head  we  may  find  that  he  lifts  the  abducted  arm  readily 
off  the  cardboard,  or  if  it  be  passively  raised  he  may  be 
able  to  maintain  it  so  (fig.  21).  Our  object  is  to  recover 
the  power  of  abduction  from  the  side  to  a  right  angle.     If 


THE    SHOULDER    REGION  63 

we  lower  the  arm  from  the  right  angle  abducted  position  to 
the  side,  the  patient  is  unable  to  abduct  to  the  right  angle, 
but  if  we  lower  it  down  to  A  C  (fig.  20),  supporting  the 
patient's  elbow  on  the  palm  of  our  hand,  it  may  be  raised 
to  the  right  angle  readily.  We  gradually  lower  the  supported 
elbow,  beginning  each  day  at  our  original  minimum  till 
finally  we  reach  the  position  with  the  arm  at  the  side.  There 
will  be  recovery  in  this  posture  when  the  patient  can  abduct 
to  the  right  angle  at  once  with  the  arm  at  the  side.  Until 
this  deltoid  arc  is  completed  the  patient  is  unable  voluntarily 


Fig.  21. — Method  of  re-educating  the  deltoid. 

to  enter  the  second  or  scapula  arc.  In  many  cases  I  have 
seen,  this  has  been  unattainable,  not  so  much  on  account  of 
the  weakened  deltoid  as  of  a  contracted  pectoralis  and  occa- 
sionally of  the  latissimus  dorsi.  The  position  of  the  forearm 
and  hand  in  testing  for  deltoid  recovery,  or  in  commencing 
re-education,  is  important.  With  outward  rotation  at  the 
shoulder,  flexion  at  the  elbow  to  a  right  angle,  and  supina- 
tion of  the  hand,  deltoid  action  is  aided  (fig.  22).  It  is  less 
easy  with  the  elbow  extended  and  the  hand  supinated.  It 
is  difficult  with  the  hand  over-pronated,  the  elbow  flexed, 
and  inward  rotation  at  the  shoulder.     In  an  old  neglected 


64  THE    ACTION    OF    MUSCLES 

case  of  infantile  paralysis,  with  associated  weakness  of 
flexors  and  extensors  giving  rise  to  "  flail  elbow/'  it  is  best 
at  first  to  fix  the  elbow  by  means  of  adhesive  plaster  in  the 


Fig.  22. — Illustrating  method  of  educating  the  deltoid. 

flexed  position,  so  as  to  improve  our  leverage  for  abduction 
movement. 

Scapula  Re-education. — The  limb  having  been  passively 
brought  into  this  arc  we  work  slowly  from  A  M  (fig.  20),  not 
from  A  E  or  A  N,  along  the  arc  M  D,  this  having  been  found 
the  easiest  position  from  which  to  begin  movement.  From 
there  we  gradually  increase  the  work  by  moving  downwards 
towards  the  plane  A  B.  The  100  units  of  work  or  maximum 
effort  are  completed  when  the  patient  can  move  the  limb 
along  the  arc  B  D.  We  cannot  work  from  A  E  to  A  D  till  we 
are  assured  of  A  M  to  A  D,  nor  similarly  from  A  N  till  we 
are  assured  of  A  E.  All  the  time  we  support  the  patient's 
extended  elbow  with  our  hand.  It  may  not  be  necessary  to 
wait  for  the  completion  of  the  deltoid  arc  before  commencing 
with  the  scapula  arc.  The  fact  that  voluntary  movement 
can  take  place  in  the  latter  enables  one  to  give  a  hopeful 
opinion  as  to  the  probability  of  recovery  of  movement  in 


THE    SHOULDER    REGION  65 

the  deltoid  arc  in  an  old  infantile  paralysis  case.  Re- 
education in  the  two  arcs  may  go  on  together,  but  we  know 
that  until  deltoid  abduction  to  a  right  angle  is  complete,  we 
cannot  lift  our  arm  from  the  side  above  the  head  in  one 
continuous  movement.  Re-education  movements  should  be 
carried  out  for  twenty  minutes  about  four  times  a  day. 
These  procedures  are  similarly  repeated  with  the  patient 
slightly  raised  by  means  of  an  ordinary  pillow  under  the 
head,  and  in  this  manner  he  is  gradually  elevated  to  the 
orthograde  or  erect  posture.  The  100  units  of  work  or 
normal  have  been  achieved  when  the  patient  is  able  sitting 
erect  to  abduct  the  arm  from  the  side  not  only  to  a  right 
angle,  but  to  elevate  it  also  above  the  head. 

As  illustrating  the  difficulties  we  may  have  in  recom- 
mencing function  and  the  various  means  adopted  in  seeking 
for  muscular  advantages,  the  case  of  an  adult  with  infantile 
paralysis  of  about  two  years'  standing  may  be  cited.  Both 
upper  limbs  had  been  affected,  and  throughout  this  period 
he  was  not  able  to  raise  either  arm  to  a  right  angle.  After 
four  weeks'  treatment  on  the  lines  of  the  preceding  principles 
he  was  able  when  lying  down  and  elevated  on  two  pillows 
to  raise  both  hands' above  the  head.  When  seen  the  patient 
was  placed  immediately  in  a  double  upper  limb  abduction 
splint.  The  right  upper  extremity  was  the  worse  of  the 
two,  and  to  this  I  shall  refer.  He  was  tested  lying  flat 
on  a  firm  table  with  a  single  pillow  under  the  head  and 
a  sheet  of  powdered  cardboard  under  the  limb,  to  obviate 
friction.  With  the  hand  at  the  side,  beyond  a  jerk  of 
2  to  3  inches  out  he  was  at  first  quite  unable  to  abduct 
the  limb.  I  then  placed  the  arm  with  the  elbow  extended 
in  the  second  arc,  i.e.  elevated  it  to  an  angle  of  about 
140  degrees,  A  E  (fig.  20),  and  found  the  patient  elevated 
it  to  180  degrees,  A  D  (fig.  20).  It  did  not  fall  to  the  side. 
With  coaxing  I  found  he  could  elevate  it  from  100  to 
180  degrees. 

As  a  result  of  this  the  opinion  of  possible  return  of  ab- 
duction power,  of  deltoid  action,  became  slightly  favourable. 
In  a  week  when  lying  flat  with  the  arm  resting  on  a  pillow 

5 


66  THE   ACTION    OF   MUSCLES 

(still  using  the  cardboard)  and  with  the  elbow  extended, 
he  was  able  to  jerk  the  limb,  and  in  this  way  to  abduct 
it  from  the  side  up  to  the  right  angle  from  which,  using 
the  pillow  as  a  support,  he  elevated  it  above  his  head 
with  ease.  One  movement  only  of  this  nature  was  at  first 
a  great  effort  for  the  patient,  but  it  represented  the  best 
means  of  antagonizing  the  more  powerful  pectoral.  It 
was  then  found  that  if  we  took  the  pillow  away  from  the 
side  so  as  to  increase  the  effort,  he  was  unable  to  elevate 
the  limb.  If  however  we  used  first  a  smaller  pillow  and 
then  a  folded  sheet  he  finally  elevated  the  arm  from  the 
side  without  pillow  support.  Gradually  in  this  position  he 
abducted  the  limb  to  the  right  angle  with  less  jerk  and  more 
true  volitional  effort.  I  found  also  that  though  there  was 
difficulty  in  elevating  with  the  elbow  extended,  yet  if  I 
flexed  the  elbow  (the  brachialis  though  functional  was  weak) , 
shortening  the  length  to  be  elevated,  the  patient  could  raise 
the  arm  from  the  side  above  the  head — at  first  with  some 
effort,  and  later  with  comparative  ease.  Within  three 
weeks  an  arm  condemned  after  nearly  two  years  as  hopeless 
for  recovery  could  be  raised  by  the  patient's  volition  from 
the  side  above  the  head  in  the  lying-down  posture  ;  and 
similarly  a  week  later  when  the  patient's  head  and  shoulders 
were  elevated  by  two  pillows.  As  the  limb  was  raised  from 
the  beginning  more  easily  with  the  elbow  flexed  than  with 
the  elbow  extended  the  line  of  treatment  was  obviously  to 
regard  the  flexed  elbow  as  the  zero — the  extended  elbow 
position  being  gradually  reached  by  means  of  a  light  splint 
or  adhesive  plaster. 

The  first  cases  of  infantile  paralysis  with  loss  of  abduc- 
tion power  I  ever  treated  by  this  method  were  a  series  of 
ten  seen  in  Australia  during  an  epidemic  of  this  disease 
in  1908.*  They  were  all  immobilized  for  from  ten  to 
fourteen  weeks,  and  of  these  nine  recovered.  They  were 
not  cases  which  could  have  recovered  spontaneously,  as 
the  improvement  was  very  gradual.      The  case  that  did 

*  "  Treatment  of  Infantile  Paralysis  of  the  Upper  Limb."  Intercol. 
Med.  Journ.  of  Aust.,  May  1909. 


THE    SHOULDER    REGION  67 

badly  was  that  of  a  child  with  four  limbs  affected  and  the 
muscles  of  the  back  and  neck,  in  addition  to  having  marked 
meningeal  symptoms.  Within  an  hour  after  being  seen  all 
cases  were  immobilized  by  means  of  the  abduction  upper 
limb  splint,  and  when  possible,  recumbency  obtained  by 
means  of  a  double  Thomas  hip  splint.  Personally  at  the 
outset  I  prefer  complete  recumbency  with  even  one  limb 
affected,  using,  not  owing  to  any  particular  virtue  for  this 
condition,  but  for  its  convenience,  the  double  Thomas  hip 
splint.  The  limb  was  well  surrounded  with  wool  and  rested 
completely  for  a  week.  At  the  end  of  that  time  the  limb 
was  taken  off  the  splint  for  purposes  of  re-education,  being 
placed  on  a  pillow  in  the  position  occupied  when  in  the 
splint.  Neither  massage  nor  electrical  treatment  was  allowed 
in  these  cases  until  recovery  in  the  erect  position  was 
reached.  Massage  does  not  initiate  muscular  function  ;  it 
does  not  permit  rest  of  an  inflamed  cell.  These  results 
were  shortly  afterwards  confirmed  by  E.  Mayer  of  Cologne, 
who  in  one  of  his  cases  with  affection  of  both  arms,  leg,  and 
back,  obtained  complete  recovery  in  two  months  except  for 
a  slight  weakness  of  the  tibialis  anticus.* 


Pectoral  Contraction  :    Stiff  Shoulder 

The  importance  of  pectoral  contraction  (occasionally  also 
that  of  the  latissimus  dorsi)  in  preventing  arm  elevation 
cannot  be  too  strongly  insisted  on.  Not  only  should  the 
arm  be  abducted,  but  rotated  backwards,  so  as  to  obviate 
all  chance  of  contraction  occurring.  Frequently  one  sees 
an  abduction  splint  applied  in  which  the  hand  is  brought 
forward  on  a  level  with  or  beyond  the  patient's  mouth, 
thus  favouring  pectoral  contraction.  In  re-education  the 
greatest  antagonistic  force  is  felt  as  we  approach  the 
right  angle  A  B  (fig.  20),  and  until  this  is  overcome 
we  may  move  readily  from  H  to  C  and  be  unable  to 
move  from  C  to  B.     The  possibility  of  a  "  stiff  shoulder  " 

*  International  Clinics,  vol.  i,    1912. 


68 


THE    ACTION    OF    MUSCLES 


following  any  injury  or  inflammation  of  the  shoulder 
region  should  always  be  borne  in  mind  and  means  taken 
to  prevent  it.  I  have  seen  it  occur  after  rheumatic 
inflammation  of  the  shoulder,  fractures  of  the  upper  end 
of  the  humerus,  falls  on  the  shoulder,  and  after  bullet 
wounds  of  the  neck  region  and  of  the  shoulder  joint  without 
much  obvious  injury  to  muscle.     By  a  stiff  shoulder  we  do 


Fig.  23.—  Stiff  shoulder. — The  patient  when  erect  is  unable  to  abduct 
the  arm  45  degrees  from  the  side. 


not  necessarily  mean  "adhesions"  in  the  joint  binding 
the  head  of  the  humerus  to  the  glenoid  cavity.  In  many 
cases  of  stiff  shoulder  the  head  of  the  humerus  can  be  rolled 
freely  on  the  glenoid.  The  two  factors  to  be  borne  in  mind 
are  adductor  contraction,  which  is  specially  favoured  by 
gravity,  and  weakness  (paresis)  of  the  muscles,  which  elevate 
the  limb.  The  former  responds  to  continued  pressure,  though 
in  an  old  case  it  may  be  necessary  to  lengthen  the  pectoral 
tendon,   and  the  paresis  will  yield   to   treatment   on  the 


Fig.  24. — When  lying  flat  on  a  firm  table  the  same  patient  abducts  the 
arm  readily  to  a  right  angle. 


Fig.  25. — When  lying  flat  the  same  patient  can  partly  elevate  the  left 
upper  limb  above  the  head,  i.e.  can  enter  the  second  or  scapula 
rotation  arc. 


681 


THE    SHOULDER    REGION  69 

previously  indicated  lines  of  gradual  re-education.  These 
cases  are  numerous.  They  have  usually  had  massage  of 
muscles  assiduously  for  many  months,  and  the  "  adhesions 
of  the  joints  "  have  at  various  times  been  broken  down 
under  an  anaesthetic  without  alleviation  of  the  condition. 
Muscular  function  as  a  factor  in  restoration  has  been 
regarded  as  unworthy  of  consideration. 

My  attention  was  first  drawn  to  these  conditions  by  the 
case  of  a  woman  who,  thirteen  months  before  being  seen, 
had  fallen  on  her  right  shoulder.  Pain,  swelling,  and  stiff- 
ness followed,  for  which  massage,  electricity,  and  forced 
movements  "  to  break  down  the  adhesions  "  were  used. 
On  examination,  in  spite  of  the  fact  that  the  head  of  the 
humerus  could  be  rotated  freely,  there  was  inability  to 
abduct  the  arm,  when  sitting,  more  than  two  inches 
from  the  side.  When  lying  down  however,  with  a  small 
pad  under  the  head,  she  was  able  to  her  astonishment 
to  abduct  the  arm  to  a  right  angle,  and  though  with 
difficulty,  owing  to  some  contraction  of  the  pectoralis, 
to  raise  it  above  her  head.  She  was  thus  not  only  able 
when  lying  down  to  complete  the  arc  H  B  (fig.  20),  but 
could  practically  complete  the  second  arc  B  D.  The  limb 
was  placed  on  the  abduction  upper  limb  splint  to  stretch 
the  adductor. 

When  the  splint  was  taken  off  a  week  later  the  patient 
was  still  unable  to  abduct  the  arm  when  sitting  up,  but 
on  lying  down  she  raised  it  above  her  head  with  ease.  In 
two  days  she  was  able  to  raise  it,  not  only  when  lying  flat, 
but  also  when  the  head  was  elevated  on  a  pillow.  Within 
a  fortnight  she  was  able  to  raise  the  hand  above  the  head 
when  sitting  up,  having  during  that  time  been  gradually 
raised  by  pillows  to  the  erect  position,  the  movements 
each  day  being  commenced  in  the  lying-down  or  "  zero  " 
position.  A  week  later  she  was  able  to  raise  the  arm 
immediately  on  sitting  up.  Till  then  the  splint  was  worn. 
Such  a  rapid  recovery  is  however  rare.  Treatment  usually 
extends  over  a  much  longer  period.  The  patient,  in  this 
as  in  all  cases  of  muscular  affection,  must  be  encouraged 


70  THE    ACTION    OF    MUSCLES 

to  take  an  intelligent  interest  in  his  or  her  own  condition  ; 
and  in  this  way  any  superadded  hysterical  or  functional 
element  in  the  case  may  be  successfully  eliminated.  With 
a  pillow  on  the  table  or  floor  for  twenty  minutes  four  times 
a  day  the  attempt  at  previous  maximum  effort  should  be 
repeated.  The  volitional  effort  of  the  patient  can  be  greatly 
aided  by  gentle  but  firm  pressure  on  the  contracted  pectoralis 
major,  and  the  patient  should  also  make  traction  with  his 
sound  hand  on  the  affected  limb.  .?< 


CHAPTER    III 

JHE      BICEPS      BRACHII     AND    BRACHIALIS  : 
MUSCULOCUTANEOUS    PARALYSIS 

The  musculocutaneous  nerve,  which  derives  its  origin 
from  the  fifth  and  sixth  cervical,  supplies  two  muscles,  the 
brachialis  and  biceps  brachii.  The  coraco-brachialis,  though 
pierced  by  the  nerve,  receives  its  supply  from  the  seventh 
cervical.  Occasionally,  it  is  stated,  an  additional  fine  branch 
can  be  traced  from  the  musculo-spiral  to  the  brachialis 
muscle.  This  is  also  derived  from  the  fifth  and  sixth 
cervical. 

Brachialis. — In  the  marsupial  this  is  a  comparatively 
small  muscle.  In  man  it  is  strong  and  fleshy.  It  arises  by 
an  extensive  and  largely  muscular  origin  from  the  lower  half 
to  two-thirds  of  the  outer  and  inner  surfaces  of  the  front  of 
the  humerus,  and  crossing  the  elbow  joint  has  its  insertion 
into  the  front  of  the  coronoid  process  of  the  ulna  (fig.  n, 
p.  53).  In  the  student's  mind  the  power  of  this  muscle  is 
over-shadowed  by  that  of  the  biceps.  The  strong  grip  of 
origin  this  muscle  has  is  well  shown  in  the  magnificent 
dissection  of  the  humerus  demonstrating  the  attachment 
of  the  different  muscles  prepared  by  William  Pearson  at 
the  London  College  of  Surgeons. 

The  brachialis  throughout  its  extent  is  essentially  a  fleshy 
muscle  compared  with  the  biceps.  The  muscular  character 
is  continued  almost  to  the  insertion,  and  in  a  well-dissected 
specimen  of  the  bend  of  the  elbow,  the  majn  biceps  tendon 
appears  as  an  insignificant  structure  compared  with  the 
broad  muscular  brachialis  in  the  background.  This  muscle 
is  the  bender  of  the  elbow  joint,  and  its  antagonist  is  the 

71 


72 


THE    ACTION    OF    MUSCLES 


triceps  (extender).  The  brachialis  instead  of  flexing  the 
forearm  on  the  arm,  in  which  case  the  arm  is  the  fixed  point, 
may  produce  the  reverse  action  and  flex  the  arm  on  the 
forearm,  in  which  case  the  forearm  is  the  fixed  point.  This 
is  seen  in  elevation  of  the  body  on  the  horizontal  bar  (fig.  26)  t 


BRACHIALIS 


TRICEPS 


BRACHIALIS 


TRICEPS 


Fig.  26. — Illustrating  "reverse  action  "  by  the  brachialis  muscle. 

the  origin  of  the  brachialis  being  the  insertion,  and  the 
insertion  the  origin.  When  the  athlete  grasps  the  bar  with 
the  hands  to  raise  himself  he  does  so  with  the  hand  either 
in  the  position  of  over-supination  or  over-pronation.  If  the 
former,  the  biceps  is  contracted  ;  if  the  latter,  it  is  relaxed 
and  elongated.     Elevation  of  the  body  really  consists  of 


THE  BICEPS  BRACHII  AND  BRACHIALIS      73 

flexion  of  the  arm  on  the  fixed  forearm — the  amount  of 
elevation  depending  on  the  degree  of  flexion.  This  action 
is  performed  by  the  brachialis,  and  the  triceps  its  opponent 
is  relaxed  and  elongated. 

The  brachio-radialis  or  supinator  longus  is  regarded  as 
an  accessory  flexor  of  the  elbow  joint.  Both  pronating  and 
supinating  powers  have  also  been  ascribed  to  this  muscle, 
the  power  therefore  of  contracting  and  relaxing  at  one  and 
the  same  time.  In  man  this  muscle  would  appear  to  be 
struggling  to  retain  its  position  in  the  forearm.  If  its  inser- 
tion be  examined  closely  in  a  well-dissected  specimen  the 
tendon  is  found  not  merely  to  be  inserted  into  the  lateral 
edge  of  the  lower  end  of  the  radius,  but  on  to  the  anterior 
surface  as  well,  it  comes  well  round  to  the  front  at  its 
insertion.  This  in  man  would  correspond  to  the  outer  more 
tendinous  portion  of  the  insertion  as  seen  in  the  wombat. 
The  centre  of  motion  for  muscles  inserted  into  the  radius 
is  radio-ulnar,  not  humero-ulnar,  and  I  regard  this  muscle 
as  an  accessory  supinator  especially  to  the  biceps. 

Its  greatest  development  is  reached  in  the  powerful  fore 
limb  of  the  wombat  (fig.  10,  facing  p. 50),  and  its  origin  reaches 
as  far  as  the  spine  of  the  scapula.  Here  it  acts  as  a  supinator, 
being  inserted  by  a  broad  attachment  into  the  outer  margin 
and  dorsum  of  the  lower  end  of  the  radius.  In  the  koala  it 
has  an  extensive  origin  from  the  humerus,  and  crossing 
dorsal  to  the  radio-carpal  articulation  is  inserted  by  a  well- 
defined  tendon  into  the  outer  side  of  the  carpus.  In  the 
poorly  developed  fore  limb  of  the  kangaroo  it  is  largely 
tendinous,  and  closely  related  below  to  the  lower  portion  of 
the  radius  where  it  terminates. 

Biceps  Brachii. — This  arises  in  man  by  two  tendinous 
heads — a  short  head  from  the  coracoid  process,  and  a  long 
head  which  arising  from  the  upper  margin  of  the  glenoid 
cavity  passes  through  the  shoulder  joint.  The  tendon  of 
the  long  head  is  narrow  and  rounded,  while  that  of  the  short 
head  is  wide.  At  its  origin  it  is  in  close  relation  with  the 
coraco-brachialis,  and  its  under  surface  of  attachment  is 
distinctly  muscular.     The  belly  of  the  short  head  is  nearly 


74 


THE  ACTION   OF  MUSCLES 


Fig.  27. — Dissection  to  show  front  of  forearm  and  hand.     Kangaroo. 
t,  Triceps,      e,  Biceps,      p,  Pronator  teres.       n,  Palmaris  longus.       r,  Flexor  carpi  radialis. 
F,  Flexor  carpi  ulnaris.       b,  Brachio-radialis.       d,  Wrist  extensors.      A,  Ext.  carpi  radialis. 


THE  BICEPS   BRACHII  AND   BRACHIALIS      75 

twice  as  extensive  as  that  of  the  long  head.  The  two  join 
about  the  junction  of  the  middle  and  lower  third  of  the  arm. 
Just  above  the  elbow  the  fibres  terminate  in  a  somewhat 
flattened  tendon  which  is  inserted  into  the  dorsal  part  of 
the  tuberosity  of  the  radius.  In  short,  the  biceps  brachii 
is  inserted  into  the  sides  of  a  rotating  cylinder. 

At  the  junction  of  the  muscular  belly  and  the  tendon  of 
insertion  we  have  arising  a  membranous  band — the  so-called 
bicipital  fascia — about  £  inch  broad  and  running  on  the 
anterior  surface  of  the  tendon  from  its  outer  to  inner  side. 
It  is  attached  to  the  deep  fascia  of  the  upper  third  of  the 
forearm.  The  bicipital  fascia  does  not  receive  the  insertion 
of  any  muscular  fibres,  and  the  direction  of  the  biceps 
tendon  from  the  inner  to  the  outer  margin  is  wholly  towards 
the  tuberosity.  This  fascia  would  appear  to  act  as  a  band 
somewhat  similar  to  the  annular  ligaments  or  folds,  and 
to  prevent  undue  prominence  with  liability  to  injury  of  a 
well-defined  tendon.  It  is  essential  that  tendons  should  be 
firmly  held  down  to  the  bone,  for  if  they  were  allowed  to 
rise  during  the  action  of  the  muscle,  the  effects  of  muscular 
contraction  would  be  greatly  interfered  with.  The  long 
head  of  the  biceps  might  almost  be  regarded  as  a  ligament 
of  the  shoulder,  serving  to  avoid  forcible  impaction  of  the 
head  of  the  humerus  against  the  coraco-acromial  arch  during 
abduction  of  the  arm.  Its  division  is  carefully  avoided  by 
surgeons  during  shoulder  joint  excision. 

Action  of  the  Biceps 

The  biceps  is  usually  regarded  as  the  great  flexor  of  the 
elbow  joint,  and  as  a  supinator  of  the  forearm.  It  is  a 
supinator  of  the  forearm,  and  so  of  the  hand,  but  does  not 
flex  the  elbow — that  function  being  performed  by  the 
brachialis.  In  the  first  place  we  would  observe  that  the 
athlete  who  displays  his  biceps  during  elbow  flexion  does 
so  with  the  hand  in  a  position  of  over- supination.  If  we 
over-pronate  the  forearm,  the  biceps  as  a  supinator  must 
be  in  a  physiological  state  of  relaxation  and  elongation. 


76 


THE  ACTION   OF   MUSCLES 


Yet  with  the  hand  over-pronated  we  readily  flex  the  elbow. 
This  action  is  due  to  the  brachialis  only.  If  when  half  way 
through  the  movement  of  flexion  we  over-supinate  the 
forearm  the  biceps  is  immediately  seen  to  contract  and 
harden  (shorten).  If  we  flex  still  further  when  over-supi- 
nated,  and  then  over-pronate,  the  biceps  is  seen  to  relax  and 
elongate.  Further,  if  the  biceps  flexed  the  forearm,  when  we 
extended  the  forearm  it  would  be  in  a  state  of  relaxation 
and  elongation,  yet  in  this  position  we  can  see  its  con- 
traction on  supinating.     Thus  the  biceps  acts  as  a  supinator 


Fig.  28. — Biceps  brachii  and  brachialis.     Biceps  in  pronation  and 
supination  of  forearm. 

in  both  the  positions  of  flexion  and  extension  of  the  elbow 
joint.  For  its  action  flexion  is  most  favourable.  The 
moment  of  its  force  is  greater  then  than  in  the  extended 
position.  These  facts  I  was  able  to  verify  in  the  case  of  a 
soldier  with  a  shell  wound  of  the  biceps  and  adherent  skin 
giving  rise  to  a  well-defined  scar  (fig.  28.)  When  the  biceps 
was  in  a  state  of  relaxation  and  elongation  the  scar  was 
level  with  the  surface,  but  when  the  muscle  contracted 
and  shortened  it  gave  rise  to  a  well-defined  pit  admitting 
the  tip  of  the  little  finger.  Both  the  pronator  teres  and 
supinator  (brevis)  cross  the  elbow  joint,  the  former  on  the 


THE    BICEPS    BRACHII    AND    BRACHIALIS      77 

ventral  aspect  and  the  supinator  more  dorsally.  As  both 
these  muscles  are  inserted  into  the  radius  the  centre  of 
motion  for  these  muscles  is  not  humero-ulnar  (elbow  joint) 
but  radio-ulnar. 

It  may  be  stated  that  muscles  inserted  into  the  radius 
do  not  cause  motion  in  the  humero-ulnar,  but  in  the  radio- 
ulnar articulation.  They  are  either  pronators  rotating  the 
radius  inwards  and  the  palm  of  the  hand  down,  or  supinators 
turning  the  radius  outwards  and  the  palm  of  the  hand 
upwards.  Their  contraction  does  not  cause  the  physiological 
state  of  relaxation  in  either  the  flexors  or  extensors  of  the 
humero-ulnar  or  elbow  joint.  Extension  of  the  elbow  joint 
is  more  favourable  for  supinator  brevis  action  and  flexion 
for  action  of  the  pronator  teres,  although  both  these  muscles 
can  act  like  the  biceps  in  the  flexed  or  extended  condition 
of  the  elbow.  The  pronator  quadratus  would  appear  to  act 
best  with  a  firm  ulna,  as  in  the  position  of  elbow  extension. 
Pronation  of  the  forearm  in  the  extended  position  is  effected 
by  the  pronator  quadratus  assisted  by  the  pronator  teres, 
and  supination  by  the  supinator  brevis  assisted  by  the 
biceps  and  brachio-radialis.  Pronation  of  the  forearm  in 
the  flexed  position  is  effected  by  the  pronator  teres  with 
possible  slight  assistance  from  the  quadratus,  and  supina- 
tion by  the  biceps  assisted  by  the  supinator  brevis  and 
brachio-radialis.  Thus,  in  flexion  the  effective  engines  are 
the  pronator  teres  and  biceps,  and  the  subsidiary  ones  the 
quadratus  and  supinator  brevis. 

It  may  be  argued  that  if  the  muscles  of  the  arm  and 
forearm  be  removed  in  a  fresh  cadaver  and  the  biceps  alone 
be  left  the  elbow  may  be  flexed  by  traction  made  on  that 
muscle — unmistakable  evidence  of  its  power  as  a  flexor. 
It  is  of  course  necessary  to  know  if  the  traction  were  made 
in  the  natural  direction.  Furthermore,  we  are  in  this  case 
taking  no  consideration  of  the  opponents  of  flexion.  Elbow 
flexion  is  ordinarily  permitted,  not  only  because  the  brachialis 
contracts  and  shortens,  but  because  the  triceps  relaxes  and 
lengthens.  The  biceps  in  the  natural  condition  is  allowed 
to  act,  not  because  the  triceps  relaxes,  but  because  the 


78 


THE  ACTION   OF  MUSCLES 


pronators  do.  Relaxation  of  the  triceps  does  not  permit  of 
supination,  although  all  anatomists  are  agreed  that  the 
biceps  has  supinating  power.  In  the  human  biceps  the 
principal  motor  force  is  that  associated  with  the  short  or 
coracoid  head,  and  the  future  line  of  evolution  would  appear 
to  be  along  the  lines  of  the  retention  of  the  long  head  or 

HUMAN    \  N.S.  WOMBAT.  N.S.  MALABAR 

SQUIRREL  N.S. 


RADIAL    INSERTION 


BRACHIAUS 


Fig.  :  9. — Nature's  experiments  with  the  biceps  brachii. 

tendon  as  a  ligament  of  the  shoulder  joint  only.  It  is 
interesting  to  note  that  in  a  case  of  infantile  paralysis  seen 
recently,  the  right  upper  limb  showed  a  function iz in g  short 
or  coracoid  portion  which  was  defined,  while  the  long  or  outer 
portion  could  not  be  demonstrated. 

In  connection  with  the  biceps,  nature  has  made  some 
interesting   experiments.     In    the   marsupial   wombat   the 


THE    BICEPS    BRACHII    AND    BRACHIALIS      79 

condition  is  as  follows.  At  the  origin  there  are  not  two 
separate  heads,  but  a  single  broad  tendon  about  2*25  cm. 
wide  passing  over  the  front  of  the  shoulder  joint.  This  is 
mainly  attached  to  the  coracoid,  but  the  outer  margin  for 
about  5  cm.  is  thick  and  tough,  and  is  traced  as  in  the 
human  type  to  the  upper  rim  of  the  glenoid  cavity.  There 
is  a  double  insertion.  The  outer  thick  part  of  the  tendon 
of  origin  is  traced  to  a  muscular  belly  (6*5  cm.  long)  which, 
terminating  in  a  small  tendon,  is  inserted  into  the  coracoid 
process  of  the  ulna  together  with  the  brachialis.  The  main 
portion  of  the  tendon  of  origin  is  traceable  to  a  larger 
muscular  belly  (9  cm.  long)  which  terminates  in  a  longer 
tendon  than  that  of  the  preceding,  and  is  inserted  into  the 
tubercle  of  the  radius.  Thus  in  the  marsupials  nature 
clearly  differentiated  between  flexion  of  the  elbow  and 
supination  of  the  forearm. 

In  the  Malabar  squirrel  (Rodentia),  I  found  that  the  short 
or  coracoid  head  was  non-existent.  Its  belly  arose  as  a 
slender  muscle  '5  cm.  wide  from  the  middle  of  the  belly  of 
the  coraco-brachialis  and  joined  the  main  belly.  This  was 
275  cm.  wide  and  was  connected  with  the  long  head,  which 
resembled  that  of  man.  There  was  a  single  tendon  of 
insertion  into  the  upper  part  of  the  radius.  I  was  interested 
and  surprised  to  notice  this  line  of  evolution,  and  proceeded 
to  correlate  this  biceps  with  the  animal's  hand.  I  found 
only  four  digits  and  no  opposable  thumb — only  a  rudi- 
mentary structure,  practically  forming  a  pad,  with  dorsally 
a  small  nail.  The  hand  was  not  destined  for  a  higher  evo- 
lution. With  the  specialization  of  biceps  function  in  man 
the  long  head,  owing  to  its  relation  with  the  shoulder  joint, 
is  obviously  at  a  disadvantage  in  supinating.  It  becomes 
involved  in  joint  disease  and  injuries  to  which  the  shoulder 
is  liable,  and  is  subject  to  displacement  interfering  with  arm 
elevation.  As  previously  stated  the  "  selection  "  trend  would 
appear  to  be  in  the  direction  of  the  retention  of  the  short 
or  coracoid  head  and  belly  ;  the  long  head  being  retained 
as  a  tendon,  and  its  muscle  belly  fortifying  the  brachialis, 
as  would  seem  to  be  suggested  in  certain  of  the  marsupials. 


80  THE   ACTION    OF    MUSCLES 

Rest  in  Musculo-Cutaneous  Paralysis 

(i)  As  the  long  head  of  the  biceps,  with  which  is  connected 
a  well-defined  muscular  belly,  is  related  to  the  shoulder 
joint  it  must  be  rested  by  placing  the  arm  in  the  abducted 
position  (fig.  30),  without  the  additional  backward  rotation 
necessary  in  deltoid  paralysis. 

(2)  The  elbow  should  be  flexed  to  a  right  angle  or  less 
so  as  to  relax  and  elongate  the  triceps.  In  this  way  we  rest 
the  brachialis. 

(3)  The  forearm  should  be  over-supinated  so  as  to  take 
strain  off  the  biceps  by  elongating  the  pronators. 

These  positions  are  simply  effected  by  means  of  the 
upper  limb  abduction  splint  with  an  over-supinated  hand- 
piece (fig!  31).  This  should  be  worn  till  complete  recovery 
has  taken  place.  ,  As  I  have  repeatedly  pointed  out  mere 
flexion  of  the  elbow  is  not  the  position  of  physiological  rest 
in  this  form  of  paralysis.  Failure  to  rest  the  biceps 
effectively  is  without  doubt  responsible  for  the  large  number 
of  cases  presenting  a  failure  in  supinating  after  injuries  of 
the  brachial  plexus. 

Method  of  Re-education 

The  ideal  recovery  for  which  we  aim  is  such,  that  when 
the  patient  sits  erect  or  stands,  not  only  can  he  bring  food 
up  to  the  mouth  (brachialis),  but  can  supinate  (biceps) 
so  as  to  place  it  in  the  mouth.  With  the  patient  lying  down 
on  a  table  or  firm  bed,  and  with  a.  small  cushion  under  the 
head,  the  splint  is  removed  and  the  limb  placed  on  a  pillow 
occupying  as  nearly  as  possible  the  position  it  occupied 
when  in  the  splint  (fig.  32).  A  sheet  of  carboard  powdered 
is  placed  under  the  limb  to  obviate  friction  in  movement. 
Thus  flexion  and  extension  take  place  on  an  even  and  level 
plane.  The  "  moment  of  force  "  of  the  brachialis,  i.e.  the 
effective  force,  is  the  amount  of  force  (P)  produced  by  its 
contraction  multiplied  by  the  perpendicular  distance  from 
its  point  of  application  to  the  fulcrum  or  elbow  joint.     This 


Fig.  30.- — Position  of  rest  in  musculo- cutaneous  paralysis. 


Fig.  31. — Method  of  rest  in  musculo- cutaneous  paralysis. 


So] 


THE    BICEPS    BRACHII    AND    BRACHIALIS      81 

is  greatest  when  the  forearm  is  at  a  right  angle  to  the  arm, 
for  in  this  position  the  muscle  acts  more  perpendicularly 
on  the  ulna  (fig.  33).  This  action  represents  a  lever  of 
the  third  order,  the  power  or  point  of  insertion  of  the 
brachialis  B  (fig.  33)  lies  between  the  weight  to  be  lifted 
(W)  and  the  fulcrum  or  centre  of  motion  (F)  in  the  elbow 
joint.  In  the  right-angle  position  the  perpendicular  B  F 
(ng-  33)  drawn  from  the  line  of  the  direction  of  the  power 
to  the  fulcrum  is  greatest  and  becomes  less,  C  F,  E  F,  if  for 


Fig.  35. — Commencing  re-education  of  the  brachialis.     Note  the  slight 
pronation  of  the  hand. 


example  the  elbow  be  extended  as  is  shown  in  fig.  33.  Thus 
flexion  movement  is  most  favourably  commenced  with  the 
elbow  at  a  right  angle  A  B  (fig.  34),  and  we  move  along  the 
arc  A  C  to  the  fully  flexed  position.  The  arc  of  extension  is 
gradually  increased,  E  B  and  H  B,  till  flexion  can  take  place 
from  full  extension  D  along  the  arc  D  A  C.  With  the 
patient  still  lying  flat  we  increase  the  amount  of  work  we 
ask  the  brachialis  to  do  by  lowering  the  elbow,  firstly  by 
means  of  a  smaller  pillow  (fig.  35),  then  a  folded  sheet, 
6 


82 


THE   ACTION   OF  MUSCLES 


and  finally  leave  it  unsupported — the  above  procedure 
being  successfully  repeated  at  each  stage,  at  first  on  the 
cardboard,  and  later  without.  During  these  procedures 
the  arm  is  kept  well  adducted. 


Fig.  33. — Biceps  and  brachialis. 


Fig.  34. — Biceps  and  brachialis. 


Having  then  ensured  recovery  in  this  position  the  patient 
is  gradually  elevated  by  means  of  pillows.  The  above 
procedure  is  adopted  with  each  elevation  till  the  erect 
posture  is  reached.  Until  this  occurs  it  is  best  to  begin 
each  day  with  the  lying-down  position.  Tested  and  treated 
in  this  way  it  is  surprising  what  an  amount  of  work  a  brachi- 
alis may  perform,  that  for  years  had  been  regarded  as  hope- 
less for  recovery. 

For  recovery  of  biceps  supination  the  patient  should  lie 
on  a  table  with  the  back  of  the  arm  resting  on  a  firm  pillow 
(fig.  36),  and  with  the  forearm  supported  by  the  attendant's 
hand,  placed  at  a  right  angle  A  B  (fig.  38).     C  represents 


Fig.  35. — Biceps  and  brachialis.     Work  for  the  brachialis  is  increased. 


Fig.  36. — Commencing  re-education  for  biceps  brachii. 

82] 


THE    BICEPS    BRACHII    AND    BRACHIALIS      83 

full  flexion  and  D  represents  full  extension.     If  we  assume 
N  (fig.  37)  represents  the  forearm  in  the  position  midway 


Fig.  37. 

between  pronation  and  supination,  P  the  position  of  over- 
pronation,  and  S  the  position  of  over-supination  the  arc 
P  S  would  represent  the  maximum  recovery.  We  place 
the  forearm  at  W  and  coax  it  to  supinate  along  the  arc  W  S.  ; 
then  from  N  to  S,  R  to  S,  and  finally  P  to  S.  (fig.  37).  Having 
ensured,  then,  recovery  with  the  arm  at  a  right  angle  we 
lower  the  forearm  to  E  (fig.  38),  we  increase  the  extension 
arc  and  repeat  the  same  procedure  along  the  plane  B  E 
(fig.  38).  Then  similarly  along  the  planes  BH  and  B  F, 
till  finally  B  D,  full  extension,  is  reached. 


H 


.f 


B 

Fig.  38. 


Lengthening  of  the  Pronator  Teres.— In  old  cases  of 
paralysed  biceps  in  which  failure  to  supinate  is  associated 
with   a   contracted  pronator  teres,   it  may  be  preferable 


84  THE  ACTION   OF  MUSCLES 

to  elongate  the  latter  at  once  by  operation  than  to  over- 
come its  contraction  by  graduated  force.  An  attempt  to 
strengthen  supination  by  muscle  grafting  might  be  recom- 
mended on  academic,  but  not  on  practical  grounds.  The 
distal  or  lower  half  of  the  muscle  can  be  explored  by 
making  a  vertical  incision  about  two  inches  long  over  the 
middle  of  the  radial  side  of  the  forearm.  It  has  to  be 
remembered  that  the  brachio-radialis  and  the  vessels  and 
nerve  lie  superficial  to  the  muscle  near  its  insertion.  I  have 
successfully  adopted  this  procedure  on  various  occasions. 


CHAPTER    IV 
MEDIAN    NERVE    PARALYSIS 

The   movements  performed   by  muscles   supplied   by  the 
median  nerve  are  : 

(a)  Pronation  of  the  forearm.  (Pronator  teres  and 
pronator  quadratus.)  The  antagonists  are  biceps,  supinator 
brevis,  and  supinator  longus  or  brachio-radialis  which 
supinate  the  forearm. 

(b)  Flexion  of  the  wrist.  (Flexor  carpi  radialis  assisting 
the  flexor  carpi  ulnaris.)  The  opponents  are  extensors 
carpi  ulnaris,  radialis  longus,  and  radialis  brevis.  The 
palmaris  longus  when  present  acts  as  an  accessory  flexor 
of  the  wrist. 

(c)  Complete  flexion  of  the  index  and  middle  fingers, 
third  phalanx  by  the  flexor  profundus,  second  phalanx 
by  the  flexor  sublimis,  first  phalanx  by  the  lumbricales. 
The  antagonists  are  the  interossei  which  extend  the  second 
and  third  phalanges,  and  the  extensor  communis  which 
extends  the  first  or  proximal  phalanx. 

(d)  Flexion  of  the  middle  phalanx  of  the  ring  and  little 
fingers  performed  by  the  flexor  sublimis,  whose  antagonists 
are  the  interossei.  Flexion  of  the  proximal  phalanx  in 
these  fingers  is  performed  by  the  lumbricales,  and  of  the 
distal  phalanx  by  the  flexor  profundus  (ulnar  nerve). 

(e)  Thumb  movements  : 

(i)  Abduction  of  the  thumb  from  the  index  finger  per- 
formed by  the  abductor  pollicis,  its  opponents  being  the 
adductores  pollicis  (ulnar  nerve). 

(2)  Flexion  of  the  proximal  phalanx.  Superficial  part 
of  flexor  brevis,  which  is  opposed  by  the  extensor  brevis 
pollicis  (musculo-spiral). 

85 


86  THE    ACTION    OF   MUSCLES 

(3)  Rotation  of  the  metacarpal  bone  on  its  axis,  by  which 
means  the  ball  of  the  thumb  is  turned  towards  the  palm  and 
so  opposition  of  thumb  to  fingers  is  permitted.  This  is 
performed  by  the  opponens  pollicis,  and  the  opponent  is 
the  long  abductor  pollicis  (extensor  ossis)  (musculo- spiral 
nerve). 

(4)  Flexion  of  the  distal  phalanx.  Flexor  longus  pollicis. 
The  opponent  is  the  extensor  longus  pollicis  (musculo-spiral). 


EXTENSOR 
LONQUS 


EXT:  B  REV  IS 


\>\%     EXT:  OSS  IS 
Y    N  (Long  abductor/ 

Fig.  39. — The  motor  forces  which  move  the  thumb. 

The  extensors  longus  and  brevis  and  the  long  abductor  are  supplied  by  the  musculo-spiral 
nerve.  The  opponens,  abductor  brevis  and  outer  head  of  flexor  brevis,  by  the  median  nerve, 
as  well  as  the  flexor  longus.  The  adductor  and  inner  head  of  flexor  brevis  are  supplied  by 
the  ulnar  nerve. 

The  Pronators. — The  two  muscles  producing  rotation 
inwards,  or  pronation  of  the  radius,  are  the  pronator  teres 
and  pronator  quadratus.  The  position  of  flexion  of  the 
elbow  is  most  favourable  for  pronator  teres  action,  and  the 
position  of  extension  for  that  of  the  quadratus.  Both  muscles 
however  can  act  in  either  the  position  of  an  extended  or  bent 
elbow.      Our  first  but  erroneous  impression  would   appear 


MEDIAN    NERVE   PARALYSIS  87 

to  be  that  these  pronators  are  scarcely  powerful  enough  to 
antagonize  the  supinators.  The  biceps  seems  a  much  more 
powerful  muscle  than  the  pronator  teres.  The  biceps  how- 
ever, like  the  brachio-radialis  (supinator  longus),  is  an 
elongate  muscle  with  a  large  amount  of  tendon  in  its  com- 
position. A  cord  six  inches  long  is  more  easily  broken  than 
a  cord  of  the  same  thickness  and  half  the  length.  The  biceps 
has  its  action  weakened  also  owing  to  its  long  head  passing 
through  the  shoulder  joint.  In  the  dissection  of  an  adult 
male  forearm  the  pronator  is  a  fleshy  somewhat  rounded 
muscle  from  its  beginning  almost  to  its  insertion.  It 
measures  about  17  cm.  long,  and  seen  anteriorly  its  width 
is  2 '5  cm.  The  pronator  quadratus  is  also  a  muscular 
muscle  with  a  width  of  about  5  cm.  Loss  of  pronation 
alone  would  be  sufficient  to  ruin  the  utility  of  the  upper 
limb.  Food  could  not  be  grasped  owing  to  the  inability 
to  rotate  the  radius  inwards  and  the  palm  of  the  hand 
downwards. 

Thumb  Opposition. — The  importance  of  the  action  of 
the  opponens  pollicis  cannot  be  too  strongly  emphasized. 
Its  loss  is  sufficient  to  ruin  the  utility  of  an  otherwise  perfect 
upper  limb.  The  power  of  opposing  the  thumb  to  the 
fingers,  necessary  for  the  finer  movements  of  grasping, 
reaches  its  highest  developments  in  man.  In  machine 
accidents  to  the  hand  every  effort  is  made  by  the  wise 
surgeon  to  avoid  amputation  of  the  thumb.  Fingers  with- 
out an  opposable  thumb1  are  of  little  use.  The  retention 
of  the  thumb  would  be  preferable  to  the  loss  of  the  middle, 
ring,  and  little  fingers.  The  thumb  represents  one  blade 
of  a  dissecting  forceps. 

Flexor  Profundus  and  Flexor  Sublimis.— The  arrange- 
ment of  the  tendons  of  these  muscles  in  the  hand  illustrates 
one  of  nature's  methods  for  giving  strength  to  muscle  near  its 
insertion.  As  the  root  of  the  finger  is  approached  the  tendon 
of  the  sublimis  (superficial)  is  grooved  below  for  the  deep 
flexor.  About  the  middle  of  the  proximal  phalanx  the 
tendon  of  the  sublimis  divides  into  two  slips,  and  between 
the  two  the  profundus  tendon  passes,  i.e.  the  sublimis  rests 


88 


THE  ACTION   OF   MUSCLES 


on  the  profundus.  Then  the  two  portions  of  the  sublimis 
reunite  below  the  profundus,  forming  a  grooved  channel 
on  which  the  deep  tendon  rests.  Finally  the  sublimis 
divides  again  into  two  slips,  each  being  inserted  into  the 
sides  of  the  middle  phalanx,  while  the  profundus  tendon 


Fig.  40. — Reciprocal  leverage  by  the  profundus  and  sublimis  to 
improve  flexion  power. 

is  inserted  into  the  base  of  the  distal  phalanx.  By  means 
of  mutual  support,  first  of  the  sublimis  on  the  profundus 
and  then  of  the  profundus  on  the  sublimis,  improvement 
of  leverage  is  effected  (fig.  40).  These  are  the  muscles  of 
coarse  flexion,  and  are  antagonized  by  the  interossei,  which 


MEDIAN   NERVE  PARALYSIS  89 

are  comparatively  short  muscles  having  a  powerful  muscular 
grip  of  origin  from  the  metacarpal  bones.  The  interossei  do 
not  have  to  accommodate  themselves  to  movements  of  the 
wrist  and  elbow  like  their  antagonists. 

Lumbricales. — These  are  usually  four  in  number,  small 
and  round,  and  were  so  named  owing  to  their  resemblance 
to  the  earth  worm.  Those  for  the  index  and  middle  fingers 
are  supplied  by  the  median  nerve  and  for  the  ring  and  little 
fingers  by  the  ulnar  nerve.  They  are  fleshy  in  character 
from  their  origin  almost  to  their  insertion,  and  are  instances 
of  muscles  connected  at  both  insertion  and  origin  with  the 
tendons  of  other  muscles.  They  arise  in  the  palm  of  the 
hand  from  the  tendons  of  the  flexor  profundus.  From 
their  origins  they  are  traced  to  the  radial  or  outer  sides  of 
the  metacarpo-phalangeal  joints  of  each  finger  and  on  to  the 
outer  side  of  the  proximal  phalanx.  At  about  the  junction 
of  the  middle  and  proximal  thirds  each  is  traced  to  the 
corresponding  interosseous  tendon  and  has  an  attachment 
to  the  phalanx  as  well.  The  action  of  the  lumbricales  is  to 
produce  flexion  at  the  metacarpo-phalangeal  articulations. 
They  antagonize  the  extensor  communis,  whose  action  is  to 
extend  at  the  metacarpo-phalangeal  joints  (fig.  54,  p.  109). 
Flexion  of  a  phalanx  is  produced  in  one  of  two  ways  :  either 
by  a  pull  on  the  palmar  surface  of  the  phalanx  (profundus 
and  sublimis),  or  by  a  pull  on  the  dorsal  surface  by  a  muscle 
whose  motor  machine  lies  on  the  front  of  the  hand  (lum- 
brical).  Owing  to  the  tendons  of  the  sublimis  and  pro- 
fundus passing  on  the  front  of  the  proximal  phalanx,  a 
palmar  attachment  of  the  lumbrical  was  not  possible.  The 
passage  of  the  lumbrical  along  the  side  of  phalanx  is  a  wise 
provision  of  nature  to  secure  unimpeded  action.  Further- 
more, the  phalanx  forms  a  rigid  support  by  means  of  which 
the  action  of  the  interosseous  as  well  as  of  the  lumbrical 
is  strengthened. 

Compared  with  the  profundus  and  sublimis  the  lumbri- 
cales are  the  muscles  of  fine  flexion  and  move  the  fingers 
with  great  rapidity.  They  are  the  muscles  mainly  con- 
cerned  in   the   quick   movements   of   the  fingers   seen   in 


90  THE  ACTION   OF  MUSCLES 

musicians,  and  for  that  reason  were  known  to  Cowper  some 
centuries  ago  as  the  musculi  fidicinales.  In  playing  the 
piano  we  relax  the  interossei  so  as  to  produce  slight  flexion 
(sublimis)  at  the  first  interphalangeal  joints — the  rapid 
movements  of  the  fingers  being  performed  at  the  metacarpo- 
phalangeal joints,  flexion  by  the  lumbricales  and  ex- 
tension by  the  extensor  communis.  The  power  has  been 
ascribed  to  the  lumbricales,  because  they  are  connected 
with  the  tendons  of  the  interossei,  of  extending  the  middle 
and  distal  phalanges  in  addition  to  flexing  the  proximal 
phalanges.  The  direction  of  their  pull  on  the  proximal 
phalanx  is  from  the  front  and  not  dorsally.  In  a  dissec- 
tion of  a  fresh  cadaver,  traction  made  on  the  lumbricales 
produces  flexion  at  the  metacarpo-phalangeal  joints  only, 
but  makes  no  impression  on  flexed  interphalangeal  joints. 
That  the  lumbricales  do  not  extend  the  middle  and  distal 
phalanges  is  also  shown  by  the  following  two  simple 
tests. 

(i)  If  we  acutely  flex  the  two  interphalangeal  joints  the 
lumbricales,  if  they  extended  these,  would  be  relaxed  and 
elongated  to  allow  the  flexor  profundus  and  flexor  sublimis 
to  act,  yet  in  spite  of  this  flexion  we  can  readily  bend  the 
metacarpo-phalangeal  joints.  This  is  performed  by  the 
lumbricales,  and  the  relaxation  at  the  interphalangeal  joints 
by  the  interossei. 

(2)  If  we  extend  at  the  metacarpo-phalangeal  joints, 
keeping  the  middle  and  distal  phalanges  bent,  the  lumbri- 
cales are  in  a  state  of  physiological  relaxation  and  elongation 
to  allow  of  contraction  and  shortening  of  the  extensor 
communis.  Yet  we  can  (action  of  the  interossei)  extend 
the  middle  and  distal  phalanges  from  acute  flexion.  If  the 
lumbricales  were  extensors  of  these,  as  is  so  frequently 
taught,  then  they  would  be  in  a  physiological  state  of  re- 
laxation and  contraction  at  one  and  the  same  time — relaxed 
to  allow  of  extension  at  the  metacarpo-phalangeal  joints  by 
the  communis,  and  contracted  to  produce  extension  at  the 
interphalangeal  joints. 


MEDIAN    NERVE   PARALYSIS 


9i 


Anatomical  Rest  in  Median  Nerve  Paralysis 

(1)  Owing  to  the  fact  that  the  long  flexor  muscles  arise 
above  the  elbow  joint  this  should  be  placed  in  the  position 
of  flexion. 

(2)  The  forearm  should  be  over-pronated  to  relax  and 
elongate  the  biceps  and  supinators,  thus  resting  the  pronators 
teres  and  quadratus. 

(3)  The  wrist  should  be  flexed  so  as  to  rest  the  affected 
flexor  carpi  radialis. 

(4)  The  thumb  should  be  flexed  at  the  interphalangeal  and 


wmmmmmm 

Fig.  41. — Position  of  rest  in  median  nerve  paralysis. 

metacarpo-phalangeal  joints,  thus  elongating  the  opposing 
long  and  short  extensors  supplied  by  the  musculo-spiral 
nerve,  and  should  be  drawn  across  the  palm  of  the  hand  to 
rest  the  opponens  and  prevent,  overaction  of  the  long 
abductor  pollicis  (extensor  ossis).  These  positions  of  the 
thumb  can  be  easily  effected  by  means  of  a  strip  of  adhesive 
plaster  (fig.  46).  The  failure  to  recognize  that  the  opponens 
represents  one  of  the  most  important  muscles  in  the  upper 
extremity  is  responsible  for  the  inutility  of  the  upper  limb 
which  is  frequently  seen  in  old  cases  of  infantile  paralysis. 
This  is  owing  to  the  fact  that  the  patient  is  unable  to  oppose 
the  thumb  to  the  fingers.     An  upper  limb  may  have  the  rest 


92  THE   ACTION   OF   MUSCLES 

of  its  musculature  perfect,  but  be  rendered  functionless  owing 
to  the  loss  of  the  opponens  pollicis. 

(5)  As  regards  the  index  and  middle  fingers,  these  should 
be  bent,  but  not  acutely;  at  the  interphalangeal  and  meta- 
carpophalangeal articulations,  since  all  the  flexors  are 
affected,  the  profundus  acting  on  the  distal  phalanges, 
sublimis  on  the  middle,  and  the  lumbricales  on  the  proximal 
ones.  In  the  case  of  the  ring  and  little  fingers,  flexion  at 
the  interphalangeal  and  metacarpo-phalangeal  joints  is  also 
advisable,  although  the  sublimis  acting  on  the  middle 
phalanges  is  the  only  muscle  affected. 

Although  I  regard  the  interossei  of  the  index  and  middle 
fingers  as  receiving  in  addition  to  branches  of  the  ulnar  some 
accessory  branches  from  the  median  nerve,  this  would  not 
alter  the  above  disposition  of  the  fingers  for  purposes  of  rest. 

In  a  case  with  combined  ulnar  and  median  affection  the 
positions  would  be  similar  to  the  above  as  regards  the  elbow, 
wrist,  and  thumb.  In  the  fingers  a  difficulty  arises,  owing  to 
the  fact  that  we  are  dealing  with  two  opposing  and  weakened 
groups  at  the  interphalangeal  joints,  namely  the  interossei 
and  flexors  profundus  and  sublimis.  The  best  position  is 
good  flexion  at  the  metacarpo-phalangeal  joints,  so  as  to 
rest  the  lumbricales  and  relax  and  elongate  the  extensor 
communis,  and  slight  flexion  at  the  interphalangeal  joints. 
As  the  flexors  recover  before  the  interossei  we  must  be 
careful  not  to  allow  flexor  contraction  to  occur,  and  thus 
interfere  with  the  recovery  of  the  interossei.  Functional 
recovery  of  the  groups  should  be  pari  passu  ;  this  ideal  may 
be  obtained  by  careful  muscle  reTeducation. 

In  a  case  with  combined  ulnar  and  musculo-spiral  affec- 
tion the  wrist  should  be  extended  (dorsi-flexed),  since 
although  the  flexor  carpi  ulnaris  is  affected,  we  have  intact 
for  flexion  the  flexor  carpi  radialis  ;  and  furthermore,  flexion 
is  more  readily  recovered  than  extension.  The  thumb 
should  be  adducted  towards  the  index  finger,  with  extension 
at  the  metacarpo-phalangeal  and  interphalangeal  joints. 
As  the  flexor  sublimis  (median  nerve)  is  intact  in  the  ring 
and  little  fingers,  and  all  the  flexors  in  the  index  and  middle 


Fig.  42. — Method  of  effecting  rest  in  median  nerve  paralysis. 


Fig.  43. — Commencing  re-education  of  pronation.     Median  nerve  paralysis 


[93 


MEDIAN    NERVE    PARALYSIS  93 

fingers  (median),  the  best  position  for  the  fingers  is  extension 
both  at  the  metacarpo-phalangeal  joints  to  rest  the  extensor 
communis,  and  at  the  interphalangeal  joints  to  rest  the 
interossei. 

In  a  case  with  combined  median  and  musculo-spiral 
affection  the  wrist  should  be  extended  (dor si-flexed),  since 
although  the  flexor  carpi  radialis  is  affected  we  have  intact 
for  flexion  the  flexor  carpi  ulnaris  ;  and  furthermore,  flexion, 
as  stated  above,  is  more  readily  recovered  than  extension. 
The  thumb  should  be  placed  across  the  palm  of  the  hand,  as 
the  opponens  is  the  most  important  thumb  muscle.  This 
means  also  flexion  at  the  metacarpo-phalangeal  joint,  but 
the  interphalangeal  joint  should  be  extended,  as  recovery 
of  the  long  extensor  is  more  difficult  than  that  of  the  long 
flexor.  In  the  case  of  the  fingers,  the  flexor  sublimis,  passing 
to  the  middle  phalanges  of  all,  is  affected,  as  well  as  the 
lumbricales  and  profundus  of  the  index  and  middle  fingers. 
As  regards  position  the  lumbricales  must  be  sacrificed  to 
the  extensor  communis.  The  most  suitable  position  is 
flexion  at  the  interphalangeal  joints  of  all  the  fingers,  to  rest 
the  flexors  profundus  and  sublimis,  with  hyper-extension  at 
the  metacarpo-phalangeal  joints  to  rest  the  extensor  com- 
munis. All  these  positions  can  be  affected  by  means  of 
the  upper  limb  abduction  splint,  with  the  hand-piece  adjust- 
able to  suit  the  different  positions  of  flexion  and  extension 
or  pronation  and  supination,  and  with  an  adjustable  hinge 
opposite  the  elbow  joint. 

Re-education  in  Cases  of  Median  Paralysis 

Pronation. — For  recovery  of  pronation  the  patient  should 
lie  on  a  table  with  the  back  of  the  arm  resting  on  a  firm 
pillow  (fig.  43)  and  with  the  forearm,  supported  by  the 
attendant's  hand,  placed  at  a  right  angle  A  B  (fig.  45). 
C  would  represent  full  flexion  and  D  full  extension. 

If  we  assume  N  (fig.  44)  represents  the  forearm  in  the 
position  midway  between  pronation  and  supination,  P  the 
position   of  over-pronation,   and  S   the  position   of  over- 


94 


THE  ACTION   OF  MUSCLES 

represent   the   maximum 


supination,  the  arc   S  P   would 
recovery,  or  ioo  units  of  work. 

We  place  the  forearm  at  R  and  coax  it  to  pronate  along 
the  arc  R  P,  then  from  N  to  P,  W  to  P,  and  S  to  P  (fig.  44). 

Having  ensured,  then,  recovery  with  the  arm  at  a  right 


Fig. 


44. 


angle  we  lower  the  forearm  to  E  (fig.  45),  thus  increasing  the 
extension  arc  and  repeat  the  same  procedure  along  the  plane 
B  E  (fig.  45).  Then,  similarly,  along  the  planes  B  H,  and  B  F, 
till  finally  B  D,  or  full  extension,  is  reached.     The  patient  is 


.-F 


B 


Fig.  45. 


gradually  elevated  by  means  of  pillows  and  these  procedures 
successively  repeated  till  the  erect  posture  is  reached. 

Wrist  Flexion. — Flexion  at  the  wrist  joint,  though  im- 
paired, is  not  lost,  as  the  flexor  carpi  ulnaris  is  intact.  We 
stimulate  the  return  of  function  in  the  flexor  carpi  radialis 
by   commencing   work   in    the   over-pronated    position    P 


Fig.  46. — Method  of  resting  (a)  and  of  re-educating  (b)  the  thumb  in 
median  nerve  paralysis. 


Fig.  47. — Re-educating  finger  flexion. 


[95 


MEDIAN  NERVE  PARALYSIS  95 

(fig.  44),  with  the  dorsum  of  the  hand  uppermost  and 
the  wrist  extended  so  as  to  improve  the  leverage  action  of  the 
carpal  flexors  ;  and  gradually  work  towards  the  mid  prone 
and  supine  position  N,  and  finally  to  the  over-supinated 
position  S.  Flexion  of  the  wrist  is  most  difficult  with  the 
palm  of  the  hand  looking  upwards. 

Thumb  Opposition  and  Flexion.— With  the  hand  in  the 
position  midway  between  pronation  and  supination,   the 
opponens  pollicis  and  flexor  brevis  pollicis  are  stimulated 
to  action  by  relaxing  slightly  the  adhesive  strapping  in 
order  to  permit  of  abduction,   and  then  encouraging  the 
patient  to  oppose  the  thumb  to  the  fingers.     The  abduction 
is  gradually  increased  (fig.  46)  till  we  can  obtain  opposition 
from  full  abduction.     The  adhesive  strapping  should  not  be 
removed  completely  till  recovery  of  opposition  takes  place, 
as  the  powerful  abductor  longus  (extensor  ossis)  and  the 
extensor  brevis  will  produce  forcible  abduction  and  extension 
of  the  thumb.     During  the  varying  degrees  of  increasing 
abduction   of    the   thumb,    the   flexor    longus    pollicis   is 
stimulated  by  grasping  the  proximal  phalanx  and  asking  the 
patient  to  flex  and  extend  at  the  interphalangeal  joint. 
.  Finger  Flexion. — Although  in  the  case  of  the  ring  and 
.little  fingers  the  sublimis  alone  is  affected  it  is  preferable  to 
work  all  the  fingers  together.     Flexion  of  the  fingers  is  best 
stimulated  by  resting  the  arm  on  a  firm  pillow  with  the 
patient  lying  down.     The  elbow  is  flexed  to  a  right  angle 
and    the    wrist    extended.     Extension    of    the    wrist    im- 
proves  leverage   by   providing   a   pulley  over  which   the 
weakened  long  flexors  can  act  (fig.  48).     In  this  way  the 
"moment  of  force"   of  the  flexors  is  increased.     Slight 
extension  of  the  fingers  is  at  first  allowed  and  the  patient 
encouraged    to    bend   them.     The   extension    is   gradually 
increased  (fig.  47)  till  we  can  flex  both  at  the  interphalangeal 
and  metacarpo-phalangeal  joints  from  full  extension.     We 
should  commence,  as  in  the  case  of  the  carpal  flexors,  with 
the  hand  in  the  over-pronated  position,  and  gradually  work 
towards  the  mid  prone  and  supine  position  (fig.  47),  and 
finally  to  the  over-supine  position.     Flexion  of  the  fingers, 


96 


THE  ACTION   OF  MUSCLES 


as  in  the  case  of  the  wrist,  is  easiest  with  the  palm  of  the 
hand  looking  downwards. 

In  some  cases  we  may  have  complete  recovery  of  the 
profundus  for  the  index  and  middle  fingers  and  of  the  sub- 
limis  for  all  the  fingers,  but  the  lumbricales  for  the  index 
and  middle  fingers  may  be  delayed  in  recovery.     Hyper- 


Fig.  48. — How  flexor  leverage  of  the  fingers  is  improved  by  extending 
(dorsi-flexing)   the  wrist. 

extension  may  then  occur  atthe  metacarpophalangeal  joints, 
due  to  over-action  of  the  extensor  communis.  This  is  treated 
by  acutely  flexing  on  a  splint  the  index  and  middle  fingers 
at  the  metacarpo-phalangeal  joints,  and  encouraging  pure 
lumbrical  action  by  asking  the  patient  to  flex  at  these  joints, 
whilst  the  interphalangeal  joints  are  extended  by  means  of 
light  straight  metal  splints. 


CHAPTER    V 

ULNAR    PARALYSIS 

The  ulnar  nerve  arises  from  the  inner  cord  of  the  brachial 
plexus — its  origin  being  traced  to  the  eighth  cervical  and 
first  thoracic  (or  dorsal)  nerves.  There  are  two  sets  of 
muscular  branches,  namely : 

(i)  Those  which  arise  in  the  forearm. 

(2)  Those  which  arise  in  the  palm  of  the  hand. 

(1)   Branches  which  arise  in  the  Forearm 

These  are  given  off  as  a  rule  immediately  the  nerve  enters 
the  forearm  and  supply  : 

(a)  The  flexor  carpi  ulnaris,  which  is  a  flexor  of  the  wrist 
and  accessory  ulnar  abductor  of  the  hand,  and  (b)  the  inner 
half  of  the  flexor  profundus  digitorum,  which  produces 
flexion  of  the  distal  phalanges  of  the  ring  and  little 
fingers.  It  is  important  to  note  that  the  origin  of  the 
flexor  carpi  ulnaris  can  be  traced  above  the  elbow  joint  to 
the  inner  or  medial  condyle,  while  the  profundus  arises 
below  the  joint — its  origin  being  from  the  upper  two-thirds 
of  the  front  of  the  ulna  as  well  as  from  the  interosseous 
membrane. 

(2)   Branches  which  arise  in  the  Hand 
These  supply  : 

(1)   Small  Muscles  of  the  Little  Finger,  viz. — (a)  Ab- 
ductor, which  passes  to  the  ulnar  side  of  the  base  of  the 
proximal  phalanx  and  abducts  the  little  finger  from  the  mid 
line,  separates  the  little  finger  from  the  ring  finger. 
7  97 


98  THE   ACTION   OF   MUSCLES 

(b)  Flexor  brevis  also  passes  to  the  ulnar  side  of  the 
proximal  part  of  the  first  phalanx  and  acts  like  the  preceding 
as  an  abductor  of  the  little  finger.  Both  these  muscles  are 
said  to  have  flexion  power  at  the  metacarpo-phalangeal 
joint. 

They  are  however  only  abductors,  since  we  can  separate 
the  little  finger  from  the  ring  if  the  metacarpo-phalangeal 
joint  be  in  the  position  of  extension. 

(c)  Opponens  or  Adductor. — This  is  inserted  into  the  meta- 
carpal bone  of  the  little  finger  on  the  inner  or  ulnar  side. 
Its  function  is  to  antagonize  or  oppose  the  little  finger  to 
the  others,  and  it  resembles  in  action  the  opponens  of  the 
thumb.  By  its  contraction  the  hollow  of  the  palm  of  the 
hand  is  deepened,  and  so  we  have  formed  what  the  older 
anatomists  called  Diogenes'  Cup. 

(2)  Small  Muscles  of  the  Thumb,  viz.— {a)  Adductores 
pollicis  (obliquus  and  transversus).  Both  these  portions 
have  a  tendinous  insertion  into  the  inner  or  mesial  side  of 
the  base  of  the  proximal  phalanx  of  the  thumb.  By  their 
action  the  thumb  is  approximated  inwards  towards  the 
index  finger. 

(b)  Deep  portion  of  the  flexor  brevis  pollicis.  This 
portion  is  inserted  into  the  ulnar  side  of  the  base  of  the 
first  phalanx  of  the  thumb.  It  is  a  bender  of  the  proximal 
phalanx  of  the  thumb  (fig.  39). 

(3)  Two  inner  Lumbricales  (third  and  fourth). — These 
pass  to  the  radial  side  of  the  ring  and  little  fingers  respec- 
tively and  bend  the  metacarpo-phalangeal  joints  of  these 
digits,  and  thus  are  the  antagonists  of  the  extensor  communis 
tendons  acting  on  these  joints. 

(4)  All  the  Inter ossei  (both  palmar  and  dorsal). — These 
fill  the  spaces  between  the  metacarpal  bones,  and  from 
their  positions  are  divided  into  two  sets,  dorsal  and 
palmar.  These  are  the  muscles  that  extend  the  middle  and 
distal  phalanges,  being  the  antagonists  of  the  flexor  sublimis 
and  flexor  profundus  ;  and  they  also  draw  the  fingers  out  or 
abduct  and  draw  them  in  or  adduct.  They  do  not  flex  at  the 
metacarpo-phalangeal  articulations.     This  is  performed  by 


ULNAR   PARALYSIS  99 

the  lumbricales.  The  dorsal  interossei  or  abductors  arise 
from  the  sides  of  adjacent  metacarpal  bones  forming  each 
interosseous  or  interbony  space.  Thus  they  are  four  in 
number.  The  first  (sometimes  called  abductor  indicis) 
lies  between  the  thumb  and  index  finger,  the  second 
between  the  index  and  middle,  the  third  between  the 
middle  and  ring,  and  the  fourth  between  the  ring  and 
little  fingers. 

Taking  the  mid  line  as  a  longitudinal  line  drawn 
through  the  middle  of  the  mesial  finger,  these  muscles 
are  abductors,  draw  the  fingers  out  from  the  mid  plane, 
and  so  their  attachment  can  easily  be  remembered.  Thus 
we  can  abduct  or  draw  our  index  finger  out  towards  the 
thumb,  and  to  secure  this  pull  the  tendon  of  the  first  dorsal 
interosseous  passes  over  the  metacarpo-phalangeal  joint 
on  its  radial  side.  The  middle  finger  can  be  moved 
(abducted)  either  towards  the  index  or  ring  fingers,  and 
so  we  find  that  the  dorsal  interossei  between  the  index 
and  middle  and  between  the  middle  and  ring  fingers  pass 
on  either  side  of  the  middle  finger.  To  abduct  the  ring 
finger,  i.e.  draw  it  from  the  mid  line  towards  the  little 
finger,  we  find  that  the  dorsal  interosseous  between  the  ring 
and  little  fingers  passes  to  the  ulnar  side  of  the  ring  finger. 
Both  the  thumb  and  little  finger  have  independent  abductors. 
For  the  thumb  we  have  the  abductor  poinds  (median 
nerve)  and  the  long  abductor  (musculo-spiral  nerve).  For 
the  little  finger  we  have  the  abductor  minimi  digiti  (ulnar 
nerve). 

There  thus  only  remain  for  consideration  the  muscles 
that  adduct  or  move  towards  the  mid  plane,  the  index,  ring, 
and  little  fingers,  as  the  middle  finger  can  be  abducted 
either  towards  the  ulnar  or  radial  side  by  the  dorsal  interossei. 
The  thumb  has  its  own  intrinsic  adduction.  This  adduction 
of  the  fingers  is  performed  by  means  of  the  palmar  interossei. 
They  are  three  in  number,  and  smaller  than  the  dorsales. 
The  fingers  naturally  incline  towards  the  mid  line,  and  a 
greater  muscular  effort  is  required  for  abduction  than  for 
adduction.     The  pull  would  obviously  be  on  the  ulnar  side 


ioo  THE  ACTION  OF  MUSCLES 

of  the  index  and  on  the  radial  side  of  the  ring  finger  and 
little  fingers.  The  muscle  to  pull  in  the  index  finger  arises 
from  the  ulnar  side  of  its  metacarpal,  and  those  for 
the  ring  and  little  fingers  arise  from  the  radial  sides  of 
their  respective  metacarpals.  Extension  of  the  proximal 
phalanges  of  the  fingers  is  performed  by  the  extensor 
communis  tendons,  and  of  the  middle  and  distal  phalanges 
by  the  interossei.  Flexion  of  the  distal  phalanges  is 
performed  by  the  flexor  profundus,  and  of  the  middle 
phalanges  by  the  flexor  sublimis.  Flexion  of  the  proximal 
phalanges  (metacarpo-phalangeal)  is  performed  by  the 
lumbricales.  The  lumbricales  do  not  assist  in  extend- 
ing the  two  distal  phalanges.  The  interossei  do  not  assist 
in  flexing  at  the  metacarpo-phalangeal  articulation.  In 
reference  to  the  action  of  the  interossei  the  following  four 
simple  tests  are  important : 

(a)  If  we  produce  acute  flexion  at  the  interphalangeal 
joints  (relaxation  of  the  interossei  and  contraction  of  the 
flexor  profundus  and  sublimis)  and  over-extension  at  the 
metacarpo-phalangeal  joints  (extensor  communis),  we  can 
flex  at  the  metacarpo-phalangeal  joints  from  over-extension. 
This  is  performed  by  contraction  of  the  lumbricales. 

(b)  We  can  extend  at  the  interphalangeal  joints  as  readily 
with  extension  as  with  flexion  of  the  metacarpo-pha- 
langeal joints.  If  the  interossei  were  flexors  of  these  joints, 
then,  in  the  state  of  extension  they  would  be  in  a  physio- 
logical state  of  relaxation,  and  so  could  not  contract  in 
order  to  produce  extension  at  the  interphalangeal  joints. 

(c)  If  we  flex  at  the  first  or  proximal  interphalangeal  joint, 
i.e.  relax  the  interossei,  the  distal  phalanx  is  quite  flaccid  on 
tapping.  Its  extension  power  is  lost.  Perform  the  same 
movement  at  the  metacarpo-phalangeal  joint  of  the  thumb 
and  we  find  that  flexion  here  does  not  affect  the  distal 
phalanx.  Its  extensor  is  a  separate  muscle,  the  extensor 
longus  pollicis. 

(d)  Abduction  and  adduction  of  the  fingers  take  place 
with  extension  of  the  two  distal  phalanges.  If  we  flex  the 
interphalangeal  joints,  relax  the  interossei,  these  actions 


ULNAR  PARALYSIS  101 

are  interfered  with  ;  and  this  is  very  marked  if  we  prevent 
the  action  of  the  extensor  communis  by  flexing  at  the 
metacarpo-phalangeal  articulation.  If  we  extend  the  fingers 
and  hold  the  index  and  middle  steady  we  can  abduct  or 
adduct  the  ring  finger  with  ease  if  it  be  extended,  but  flex 
at  the  interphalangeal  joints  and  these  movements  are  lost. 
Abduction  or  adduction  is  with  extension  the  result  of 
interosseous  muscle  contraction.  If  we  take  for  example 
the  movement  of  abduction  of  the  ring  finger,  extension 
of  the  distal  phalanges  would  depend  on  the  contraction 
of  the  abductor  or  dorsal  interosseous,  since  the  adductor 
or  palmar  interosseous  would  be  relaxed  to  admit  of  the 
movement. 

The  long  tendons  of  the  interossei  are  placed  lateral  to  the 
proximal  phalanges  which  give  them  an  attachment.  Trac- 
tion on  these  would  be  lateral  (abduction  or  adduction). 
These  tendons  are  connected  on  the  dorsum  of  the  proximal 
phalanges  to  the  extensor  communis  tendons  by  fibrous 
membrane — thin  proximally,  thicker  more  distally.  The 
motor  engines  (muscles)  of  the  interossei  have  no  direct  pull 
on  the  common  tendons.  The  interossei  tendons  cross  the 
first  inter-phalangeal  joints  laterally,  then  pass  to  the  dor- 
sum of  the  middle  phalanges  which  give  them  an  attach- 
ment— the  tendons  of  each  side  having  a  strong  fibrous 
connection.  The  tendons  converge  and  are  attached  to- 
gether on  the  dorsum  of  the  proximal  parts  of  the  distal  or 
third  phalanges  (fig.  56,  p.  115). 

Anatomical  Rest  in  Cases  of  Ulnar  Paralysis 

(1)  As  the  flexor  carpi  ulnaris  arises  above  the  elbow  joint 
flexion  of  the  elbow  is  preferable,  and  this  can  be  simply 
effected  by  means  of  a  sling,  but  best  by  the  abduction 
arm  splint. 

(2)  The  wrist  joint  should  be  flexed  (palmar  flexion)  to 
take  all  strain  off  the  flexor  carpi  ulnaris,  and  the  hand 
should  be  diverted  towards  the  ulnar  side  to  prevent  radial 
deviation. 


102  THE  ACTION   OF  MUSCLES 

(3)  The  thumb  should  be  brought  across  the  palm  of  the 
hand  by  means  of  a  strip  of  plaster,  so  as  to  rest  the  flexor 
brevis  and  adductores  pollicis  (fig.  46).  The  importance  of 
this  cannot  be  too  strongly  insisted  on,  since  failure  to  adduct 
means  an  impairment  of  opposition  of  thumb  to  ringers. 

(4)  In  resting  the  fingers  we  have  to  consider  the  two 
inner  tendons  of  the  flexor  profundus  or  benders  of  the  distal 
phalanges  of  the  ring  and  little  fingers  at  the  second  or 
distal  interphalangeal  joint ;  all  the  interossei  or  extensors 
of  the  two  distal  phalanges  of  all  the  fingers  ;  and  the  two 
inner  lumbricales  or  benders  at  the  metacarpo-phalangeal 


Fig.  49. — Position  of  rest  for  the  upper  extremity  in  ulnar  paralysis. 

joints  of  the  little  and  ring  fingers.  The  lumbricales  are 
rested  by  flexing  the  fingers  at  the  metacarpo-phalangeal 
joints ;  it  is  preferable  to  rest  all  four,  although  only 
the  inner  two  are  affected.  In  the  case  of  the  index  and 
middle  fingers  rest  of  the  interossei  is  secured  by  extension 
at  the  interphalangeal  joints,  as  we  have  no  profundus 
to  be  considered.  In  the  case  of  the  ring  and  little  fingers 
we  have  to  choose  between  rest  of  the  profundus  by 
bending  at  the  distal  interphalangeal  joint,  which  means 
elongating  the  interossei,  or  extending  at  the  interphalan- 
geal joints  so  as  to  rest  the  interossei. 

As  the  sublimis  is  normal  (median  nerve)  in  the  ring  and 
little  fingers,  and  as  we  are  resting  other  benders,  viz.  the 


ULNAR    PARALYSIS  103 

lumbricales,  there  should  be  no  hesitation  in  regarding  the 
interossei  as  suitable  for  rest  in  preference  to  the  flexor 
profundus.  In  any  case  of  ulnar  paralysis  it  is  not  any 
failure  to  bend,  but  the  failure  to  extend  at  the  two  inter- 
phalangeal  joints  that  causes  difficulty.  The  positions  for 
rest  in  ulnar  paralysis  then  would  be  : 

(1)  Flexion  at  elbow. 

(2)  Palmar  flexion  of  the  wrist. 

(3)  Thumb  adducted  across  the  palm  of  the  hand. 

(4)  Fingers  bent  at  the  metacarpo-phalangeal  joints,  and 

extended  at  the  interphalangeal  joints. 

(5)  The  hand  midway  between  pronation  and  supina- 

tion. 

These  positions  can  be  effected  by  means  of  the  upper 
limb  abduction  splint.  This  is  hinged  at  the  elbow,  flexion 
being  adjusted  by  means  of  a  screw  or  other  mechanism. 
Adjustments  can  also  be  provided  for  the  hand-piece  by 
means  of  which  flexion  and  extension  of  the  wrist  and 
pronation  and  supination  of  the  forearm  are  regulated.  With 
recovery  of  flexion  the  wrist  is  extended  to  the  mid  position, 
and  similarly  with  the  metacarpo-phalangeal  joints.  This 
form  of  splint  is  best  worn  till  recovery  has  taken  place. 

Methods  of  Re-education  in  Ulnar  Paralysis 

Flexion  at  the  wrist  joint,  though  impaired,  is  not  lost, 
as  the  flexor  carpi  radialis  is  intact.  We  stimulate  the 
return  of  the  function  in  the  flexor  carpi  ulnaris  by  com- 
mencing work  in  the  over-pronated  position  P  (fig.  50),  the 
dorsum  of  the  hand  being  uppermost  and  the  wrist  dorsi- 
flexed.  This  improves  the  leverage  action  of  the  carpal 
flexors,  and  we  gradually  work  through  F  and  R  towards  the 
mid  prone  and  supine  position  N,  and  finally  to  the  over- 
supinated  position  S  through  D  and  W.  Flexion  of  the 
wrist  is  most  difficult  with  the  palm  of  the  hand  looking 
upwards. 

Re-education  to  regain  ulnar  abduction  should  be  carried 


104 


THE    ACTION    OF    MUSCLES 


out  with  the  hand  in  the  position  midway  between  flexion 
and  extension,  i.e.  on  a  level  with  the  forearm. 

The  action  of  the  small  muscles  of  the  thumb  is  encouraged 
by  gradually  allowing  the  thumb  to  abduct  by  relaxing  the 
adhesive  plaster.  It  is  a  mistake  to  remove  this  completely 
until  recovery  takes  place,  as  the  powerful  abductor  longus 


Fig.  50. 


pollicis  (extensor  ossis)  and  the  extensor  brevis  will  produce 
forcible  abduction  and  extension  of  the  thumb  (fig.  46). 

For  re-education  of  the  adductor  the  hand  should  rest 
on  the  table  with  the  palm  upwards,  in  the  over-supinated 
position  ;  and  for  the  flexor  brevis  in  the  position  midway 
between  pronation  and  supination. 

The  inner  lumbricales  are  stimulated  to  work  by  encour- 
aging flexion  at  the  metacarpophalangeal  joints  of  all  the 
fingers — the  interphalangeal  joints  being  maintained  in 
the  position  of  extension  by  means  of  small  straight  finger 
splints.  Until  recovery  is  complete  flexion  of  the  two  inner 
metacarpo-phalangeal  joints  should  be  insisted  upon,  as 
only  in  this  way  is  hyper-extension  at  these  articulations 
due  to  action  of  the  unopposed  communes  tendons  avoided. 
This  hyper-extension  is  unfortunately  a  common  feature  of 
ulnar  paralysis. 

The  weakness  of  the  interossei  is  shown  in  the  inability 
to  extend  at  the  interphalangeal  joints.  In  what  is  usually 
demonstrated  as  a  typical  case  of  ulnar  paralysis  the  condi- 
tion is  a  flexion  at  the  proximal  interphalangeal  joints,  and 


ULNAR    PARALYSIS  105 

a  hyper-extension  at  the  metacarpo-phalangeal  joints  of  the 
ring  and  little  fingers.  There  is  no  doubt  that  even  after 
total  division  of  the  nerve  and  subsequent  suture,  recovery 
of  the  interossei  of  the  middle  and  index  fingers — the  power 
to  extend  at  the  interphalangeal  joints — is  more  rapid  than 


Fig.  51. — Partial  ulnar  paralysis. 
The  interossei  of  the  index  and  middle  fingers  have  recovered.  The  interossei  of  ring  and 
little  fingers  are  still  paralysed.  There  is  inability  to  extend  at  the  interphalangeal  joints 
of  these  fingers  (interossei)  ;  also  inability  to  flex  at  the  metacarpo-phalangeal  joints  owing 
to  paralysis  of  the  inner  lumbricales.  The  fingers  are  flexed  at  the  interphalangeal  joints 
owing  to  action  of  the  flexores  profundis  and  sublimis. 

in  the  case  of  the  ring  and  little  fingers  (fig.  51).  One 
might  have  expected  the  reverse,  since  in  these  two  fingers 
the  opposition  of  the  flexor  profundus  is  present,  and  also 
the  lumbricales,  whilst  these  are  lost  in  the  ring  and  little 


job  THE    ACTION    OF    MUSCLES 

fingers.  At  first  I  was  inclined  to  regard  the  good  result 
in  the  case  of  the  index  finger  as  in  some  way  associated 
with  the  extensor  indicis,  but  careful  dissections  demon- 
strated that,  like  the  communis  tendon  for  the  index  finger, 
its  motor  effect  did  not  extend  beyond  the  proximal  phalanx. 
The  next  explanation  that  suggested  itself  was  :  Could 
it  be  due  to  stimulated  function  on  the  part  of  accessory — 
if  minute — branches  of  the  median  nerve  to  the  outer 
interossei  ?  Of  this  I  have  no  evidence  in  my  notes  carried 
over  a  period  of  twelve  years  in  the  dissecting  room.  Another 
explanation  was  that  recovery  of  the  interossei  would  mani- 
fest itself  earliest  and  strongest  in  the  fingers  functionally 
the  most  active.  In  the  causation  of  this  condition  two 
other  factors  must  be  taken  into  consideration.  With 
hyper-extension  at  the  metacarpo-phalangeal  joints  of  the 
ring  and  little  fingers  (over-action  of  communis  and  para- 
lysis of  lumbricales)  there  is  an  alteration  in  the  line  of  pull 
of  the  interossei,  which  becomes  angular  instead  of  straight. 
Furthermore,  an  extended  proximal  phalanx  would  form  a 
rigid  dorsal  support  for  the  sublimis  tendon,  thus  increasing 
its  flexion  pull. 

Having  as  I  thought  exhausted  all  possible  explanations  an 
interesting  phenomenon  was  noted  four  months  after  opera- 
tion in  a  case  of  complete  division  of  the  median  and  ulnar 
nerves  in  the  arm  of  a  patient  at  the  Military  Orthopaedic 
Hospital,  Shepherd's  Bush.  The  operation,  which  was  per- 
formed by  Lieutenant  Teece,  R.A.M.C,  consisted  in  a  repair 
of  the  ulnar  nerve  with  a  portion  of  the  internal  cutaneous 
and  of  the  median  with  a  portion  of  the  great  sciatic  from  an 
amputation  stump.  After  the  operation  Lieutenant  Teece 
kindly  handed  me  over  the  case  for  observation  and  re- 
education. We  were  dealing  with  a  condition  in  which 
as  regards  all  the  fingers  flexion  power  was  lost  as  well  as 
extension  of  the  middle  and  distal  phalanges.  Recovery 
of  power  in  the  fingers  was  first  obtained  in  the  flexor 
sublimis,  with  ability  to  bend  all  the  fingers  at  the  first 
interphalangeal  joint.  This  was  median  nerve  recovery. 
As  this  flexor  power  increased  it  was  noticed  that  there  was 


ULNAR    PARALYSIS 


107 


comparatively  easy  extension  at  the  interphalangeal  joints 
(interossei)  of  the  index  and  middle  fingers,  but  in  the  ring 
and  little  fingers  this  was  practically  absent,  owing  to  flexor 
contraction.  It  was  clear  that  if  this  were  not  prevented 
the  marked  deformity  of  flexor  contraction  of  the  ring  and 
little  fingers  characteristic  of  ulnar  paralysis  would  be 
manifested.  I  may  mention  that  the  pronators  were  at 
this  time  acting  strongly. 

If  all  the  interossei  had  a  similar  nerve  supply  there 
was  no  reason  why  the  two  inner  interossei  should  have 


Fig.  52.- — Testing  and  commencing  re-education  in  weakness  of  the 
extensors  of  the  fingers  (interossei  and  extensor  communis). 


behaved  differently  from  the  two  outer  ones.  There  could 
to  my  mind  be  only  one  explanation,  namely,  that  the 
median  as  well1  as  the  ulnar  nerve  was  sending  branches 
to  the  interossei  of  the  index  and  middle  fingers.  These 
interossei,  therefore,  have  a  double  nerve  supply,  of  which 
the  ulnar  forms  the  principal  portion,  since  though  at  the 
outset  of  ulnar  paralysis  we  meet  with  weakness  of  the 
outer  interossei  this  is  not  noticeable  in  cases  of  median 
paralysis.  I  have  dealt  rather  particularly  with  this 
question  because  it  is  an  important  example  of  the  value  of 
functional  anatomy  as  the  great  guiding  factor  in  the  display 
of  any  dissection.     Another  example  may  be  also  noticed 


io8 


THE    ACTION    OF    MUSCLES 


in  the  occasional  double  supply  of  the  profundus  tendon 
to  the  middle  finger.  This  is  observed  in  some  cases  of 
median  paralysis.  In  re-education  of  the  interossei  it  is 
important  not  to  take  the  fingers  out  of  the  splint  un- 
supported, as  the  sublimis  is  always  ready  to  flex  acutely, 
and  how  can  weakened  interossei  act  against  an  unrestrained 
flexor  sublimis  ?  The  fingers  are  best  kept  rested  on  an 
adjustable  metal  splint,  and  a  little  flexion  allowed  at  the 
interphalangeal  joints,  so  as  to  offer  a  minimum  effort  in 
extension.     This  is  gradually  increased  as  recovery  takes 


Fig.  53. — Increasing  the  work  of  the  extensors  of  the  fingers 

place.  The  maximum  recovery  or  100  units  of  work  has 
taken  place  when  the  interossei  can  extend  the  two  inter- 
phalangeal joints  from  acute  flexion  against  gravity,  the 
hand  being  over-pronated,  the  palm  looking  downwards 
and  the  dorsum  upwards.  Hence  in  commencing  work  for 
the  interossei  the  hand  should  be  at  first  over-supinated 
(fig.  52)  ;  by  this  means  we  obtain  gravitational  assistance. 
With  recovery,  just  as  in  re-educating  the  wrist  extensors, 
we  gradually  work  to  the  mid  prone  and  supine  position 
(fig.  53),  and  finally  to  the  position  of  over-pronation. 

As  regards  weakened  extension  of  fingers,  whether  of  the 
interphalangeal  joints  (interossei)  or  metacarpo-phalangeal 
(ext.  communis),  it  is  important  to  remember,  as  previously 


ULNAR    PARALYSIS 


109 


stated,  that  this  is  aided  by  flexion  of  the  wrist,  whether  the 
position  of  the  forearm  be  that  of  pronation,  or  supination, 
or  midway  between  the  two.  The  position  of  extension 
of  the  wrist  favours  flexion  of  the  fingers.  Thus  in  testing 
for  recovery  of  the  interossei  or  extensor  communis  the 
wrist  should  be  slightly  flexed  and  the  forearm  placed  in 
a  position  of  over- supination.  Increased  work  is  given  by 
gradually  extending  at  the  wrist  to  the  position  of  complete 
extension.     It  is  frequently  found  that  movement  of  the 


Fig.  54. — Partial  ulnar  paralysis. 

The  interossei  of  the  index  and  middle  fingers  have  recovered,  and  the  two  outer  lumbricales 
are  producing  flexion  of  these  fingers  at  the  metacarpo-phalangeal  articulations.  The  tn- 
terossei  and  lumbricales  of  the  ring  and  little  fingers  are  paralysed.  There  is  hyper- extension 
at  the  metacarpo-phalangeal  joints  owing  to  action  of  the  extensor  communis  from  paralysis 
of  the  lumbricales.  In  spite  of  strong  action  of  the  flexor  sublimis  the  patient  is  unable  to 
bend  the  proximal  phalanges. 


interossei  is  aided  by  making  pressure  on  the  proximal 
phalanges  of  the  patient. 

In  cases  where  hyper-extension  at  the  metacarpo-phalan- 
geal joint  of  the  ring  and  little  fingers  has  unfortunately 
(fig.  54)  been  allowed  to  occur,  we  find  that  the  patient  can 
extend  at  the  interphalangeal  joints  when  the  metacarpo- 
phalangeal joints  are  flexed,  but  fails  when  they  are  extended. 


no  THE   ACTION    OF   MUSCLES 

Hence  when  re-educating  the  interossei  on  the  splint  we 
should  begin  with  flexion  at  the  metacarpo-phalangeal 
joints,  gradually  extending  them  as  recovery  takes  place. 

It  must  be  borne  in  mind  that  it  is  common  enough 
to  find  sublimis  contraction  with  flexion  at  the  first  inter 
phalangeal  joints  as  a  result  of  neglect  to  rest  the  inter- 
ossei properly.  I  have  never,  on  the  other  hand,  seen  any 
impairment  to  sublimis  function  follow  when  this  treatment 
has  been  carried  out.  After  the  operation  of  suture  for 
complete  division  of  nerve  there  is  no  reason  why  movements 
should  not  be  tested  for  and  encouraged  as  soon  as  the  sur- 
gical state  of  the  wound  is  regarded  as  satisfactory.  This 
would  apply  to  the  case  of  division  of  any  nerve  in  the  upper 
or  lower  limb. 


CHAPTER    VI 
MUSCULO-SPIRAL   PARALYSIS 

The  musculo-spiral  nerve  which  supplies  the  extensors  of 
the  elbow,  the  wrist,  thumb,  and  metacarpo-phalangeal 
joints  of  the  fingers  as  well  as  the  supinator  brevis,  may  be 
regarded  as  a  continuation  of  the  posterior  cord  of  the 
brachial  plexus.  It  takes  its  rise  from  the  fifth,  sixth, 
seventh,  and  eighth  cervical  nerves.  The  order  and  position 
of  origin  of  the  muscular  branches — a  knowledge  of  which 
is  important  in  cases  of  nerve  injury — are  as  follows  : 


Triceps  and  anconeus  (extensors  of 
elbow) 


All  branches  to  these  are  given  off 
above  lower  third  of  the  arm. 


Brachio-radialis  (accessory  supinator 
of  forearm) 

Extensor  carpi  radialis  longus  (exten- 
sor and  radial  abductor  of  hand 
at  wrist  joint) 


These  muscles  arise  from  the 
main  trunk  of  the  musculo-spiral 
immediately  above  the  elbow 
joint.  The  remaining  branches 
arise  from  the  posterior  inter- 
osseous division. 


Extensor  carpi  radialis  brevis  (extensor  and  radial 
abductor  of  hand  at  wrist  j  oint) 

Supinator  brevis  (supinator  of  forearm) 

Extensor  communis  digitorum  (extender  of  meta- 
carpo-phalangeal joints  of  fingers) 

Extensor    minimi    digiti    (accessory    extender  of 
metacarpo-phalangeal  joint  of  little  finger) 

Extensor  carpi  ulnaris  (extender  and  ulnar   ab- 
ductor of  hand  at  wrist  joint) 

in 


Immediately  below 
the  elbow,  just  before 
the  posterior  inter- 
osseous nerve  enters 
.the  supinator  brevis. 


In  the  upper  third  ct 
forearm,  immediate! , 
below  the  supinator 
brevis. 


In  the 
middle     of 
the  forearm. 


112  THE    ACTION    OF    MUSCLES 

Extensor  ossis  metacarpi  pollicis  (long  abductor  of  thumb) 
or  abductor  longus  pollicis 

Extensor  brevis  pollicis  (extender  of  the  metacarpo- 
phalangeal joint  of  thumb) 

Extensor  longus  pollicis  (extender  of  the  interphalangeal 
joint  of  thumb) 

Extensor  indicis  (accessory  extender  of  metacarpo- 
phalangeal joint  of  index  finger) 

It  is  important  to  note  that  the  extensors  of  the  wrist, 
extensor  carpi  radialis  longus,  extensor  carpi  radialis  brevis, 
and  extensor  carpi  ulnar  is,  all  arise  above  the  elbow  joint, 
being  traced  to  the  lateral  or  external  condyle — the  longus, 
the  highest  in  origin  of  all,  arising  from  the  supra-condyloid 
ridge. 

The  extensor  communis  digitorum  and  the  extensor  min. 
(quinti)  digiti — really  a  portion  of  it — also  arise  above  the 
elbow  joint  from  the  outer  condyle  of  the  humerus.  The 
three  extensors  of  the  thumb,  namely,  extensor  ossis  or  long 
abductor  which  is  inserted  on  the  radial  side  of  the  base  of 
the  first  metacarpal,  the  extensor  brevis  pollicis  which  is 
inserted  into  the  dorsal  aspect  of  the  base  of  the  first  phalanx, 
and  the  extensor  longus  pollicis  which  is  inserted  into  the 
dorsal  aspect  of  the  base  of  the  second  or  distal  phalanx, 
together  with  the  extensor  indicis — constituting  the  deep 
layer  of  the  muscles  of  the  forearm — all  arise  below  the 
elbow-joint.  No  branches  are  distributed  from  the 
musculo-spiral  nerve  to  the  small  or  intrinsic  muscles  of 
the  hand.  They  receive  their  supply  from  the  median  and 
ulnar  nerves. 

The  triceps,  the  antagonist  of  which  is  the  brachialis,  is 
not  often  affected  in  paralysis.  It  is  a  powerful  muscle,  and 
its  strength  is  shown  by  the  projection  of  the  olecranon,  into 
which  its  tendon  is  inserted. 

Just  as  the  biceps  is  the  most  powerful  supinator  in  the 
flexed  position  of  the  forearm,  so  is  the  supinator  brevis 
the  most  powerful  supinator  in  the  extended  position.  This 
interesting  distinction  can  be  made  in  cases  of  musculo- 
spiral  affection  in  the  arm,  or  in  cases  of  musculo-cutaneous 
paralysis. 


MUSCULO-SPIRAL   PARALYSIS  113 

The  short,  fleshy,  and  powerful  supinator  brevis  is  traced 
above  to  the  lateral  condyle  of  the  humerus,  and,  passing 
from  behind  forwards  round  the  outer  side  of  the  upper 
portion  of  the  radius,  is  inserted  into  the  front  and  outer 
aspects  of  that  bone  as  low  down  as  the  junction  of  the 
middle  and  upper  thirds. 

The  specialization  of  thumb  movement  in  the  human 
hand  is  well  shown  in  the  fact  that  the  metacarpus,  first 
phalanx,  and  second  phalanx  have  each  a  separate  extend- 


Fig.  55. — Musculo- spiral  paralysis  (Charles  Bell). 

Note  the  over-pronated  forearm  with  elbow  extension,  wrist  flexion,  thumb  flexed  and 
adducted,  flexion  of  metacarpo- phalangeal  joints  of  the  fingers  (lumbricales).  Extension 
can  still  be  produced  at  the  interphalangeal  joints  by  the  interossei,  as  is  shown  in  the  case 
of  the  middle  finger. 

ing  muscle.  In  cases  of  thumb  drop  with  paralysis  of  all 
three,  should  tendon  transplantation  be  decided  on  it  would 
be  better  to  graft  on  to  the  extensor  ossis  (abductor)  in 
preference  to  either  the  long  or  short  extenders.  From  the 
point  of  view  of  utility,  paralysis  of  the  three  extenders  is 
not  so  severe  as  the  loss  of  the  power  of  opposition  of  thumb 
to  fingers  due  to  paralysis  of  the  opponens  pollicis. 

With   reference   to   the   abduction   power   of   the   three 
extensors  of  the  wrist,  the  extensor  carpi  ulnaris  and  exten- 
sors carpi  radialis  longus  and  brevis,  it  would  appear  that 
8 


ii4  THE    ACTION    OF    MUSCLES 

abduction,  either  to  the  radial  side  or  to  the  ulnar,  can  only- 
take  place  when  the  extensors  and  flexors  of  the  wrist  are 
in  a  state  of  physiological  equilibrium  as  regards  flexion  and 
extension.  Thus  we  can  abduct  readily  to  the  ulnar  side  by 
the  action  of  the  flexor  and  extensor  carpi  ulnaris  when  the 
forearm  and  hand  are  on  a  level,  and  similarly  to  the  radial 
side  by  the  action  of  extensor  carpi  radialis  longus  and  brevis 
and  the  flexor  carpi  radialis.  If  we  acutely  flex  the  wrist 
(palmar  flexion),  in  which  case  the  flexors  are  in  a  physio- 
logical state  of  contraction  and  the  extensors  physiologically 
relaxed  ;  or  acutely  extend  (dorsal  flexion),  in  which  case 
the  extensors  are  contracted  and  the  flexors  physiologically 
relaxed,  we  are  unable  to  perform  this  movement.  The 
effort  to  perform  this  is  then  made  by  pronation  and 
supination  of  the  forearm  and  abduction  and  adduction  of 
the  fingers.  The  practical  importance  of  this  is  in  connec- 
tion with  re-education  for  either  ulnar  or  radial  deviation 
of  the  hand.  This  should  be  carried  out  with  the  hand 
midway  between  flexion  and  extension,  on  a  horizontal 
level  with  the  forearm. 

Extensor  Communis  Digitorum. — Much  obscurity  sur- 
rounds the  action  of  this  muscle,  for  which  there  would 
appear  to  be  little  justification.  It  arises  above  the  elbow 
from  the  outer  condyle,  has  a  thick  fleshy  belly,  and  at 
the  lower  part  of  the  dorsal  aspect  of  the  forearm  divides 
into  three,  sometimes  four,  tendons.  These  tendons  diverge 
across  the  back  of  the  hand,  and,  if  only  three  exist,  the 
inner  one  divides  into  two,  one  for  the  ring  and  one 
for  the  little  finger.  The  tendon  for  the  ring  finger  is  con- 
nected to  that  for  the  little  and  middle  fingers,  but  not  to 
the  first  finger,  by  accessory  bands  or  vincula,  so  that  while 
extension  of  the  ring  finger  is  associated  with  that  of  the 
other  two,  there  is  free  mobility  of  the  index  finger.  On 
the  dorsum  of  each  proximal  phalanx  each  tendon  is  usually 
described  as  forming  an  aponeurotic  expansion,  which  is 
reinforced  by  the  tendons  of  the  lumbricales  and  interossei 
— that  of  the  index  finger  being  reinforced  by  the  extensor 
indicis    and  of  the  fifth  finger  by  the  extensor  minimi 


MUSCULO-SPIRAL    PARALYSIS 


ii5 


( quint i)  digiti.  The  expansion  then  divides  into  three 
portions,  a  central  inserted  into  the  middle  phalanx,  and 
two   lateral  ones  which  unite  and  are  inserted  into   the 


INTEROSSEOUS 
TENDON 


LUMBRlCAL 


DISTAL    INTERPHALANGEAL 
JOINT 


PROXIMAL  INTER  PHALANGEAL 
JOINT 


EXTENSOR    COMMUNIS 
TENDON 


METACARPAL.' 
PHALANGEAL 
JOINT 


INTEROSSEOUS 


INTEROSSEOUS 


Fig.   56. — The  arrangement  of  motor  forces  on  the  dorsum 
of  the  finger. 

distal  phalanx.  Thus,  from  this  description  the  communis 
when  it  contracted  would  act  on  all  the  phalanges  producing 
extension,  and  being  assisted  in  the  case  of  the  middle  and 


n6  the  action  of  muscles 

distal  phalanges  by  the  interossei  and  lumbricales.  That 
this  description  of  function  is  erroneous  can  be  demonstrated 
by  two  simple  tests. 

(a)  If  we  hyper-extend  at  the  metacarpo-phalangeal  joints 
we  can  at  the  same  time  acutely  flex  at  the  interphalangeal 
joints.  The  hyper-extension  at  the  metacarpo-phalangeal 
joints  is  due  to  the  fact  that  the  extensor  communis  is  in 
a  physiological  state  of  contraction.  If  this  muscle  ex- 
tended the  middle  and  distal  phalanges  also,  then,  to  allow 
acute  flexion  of  the  interphalangeal  joints  by  the  profundus 
and  sublimis,  the  communis  must  be  in  a  state  of  physio- 
logical relaxation  and  subsequent  elongation.  But,  as  has 
been  explained  above,  a  muscle  cannot  be  in  two  physiological 
states,  contraction  and  relaxation,  at  one  and  the  same  time. 

(b)  If  we  flex  at  the  metacarpo-phalangeal  joints  the 
communis,  which  extends  these,  must  be  in  a  physiological 
state  of  relaxation  with  subsequent  elongation,  yet  with 
these  joints  flexed  we  can  fully  extend  at  the  interphalangeal 
joints.  The  extensor  communis  produces  extension  at  the 
metacarpo-phalangeal  j  oints.  It  does  not  produce  extension 
at  the  interphalangeal  joints. 

If  we  examine  the  dorsum  of  a  proximal  phalanx,  for  ex- 
ample of  the  ring  finger  (fig.  56),  the  extensor  tendon  does 
not  spread  out  into  an  aponeurosis.  On  the  contrary,  it  is 
well  defined,  and  is  traced  mesially  to  the  distal  part  of  the 
phalanx,  where  it  is  attached.  The  motor  effect  of  con- 
traction of  the  communis  terminates  there.  Laterally  we 
see  the  two  well-defined  tendinous  edges  of  the  interossei 
receiving  on  the  radial  side,  just  distal  to  the  metacarpo- 
phalangeal joint,  the  insertion  of  the  lumbrical — and  these 
are  traced  on  to  the  distal  phalanx.  On  the  dorsum  of  the 
proximal  phalanx  these  lateral  tendons  are  connected 
proximately  to  the  communis  tendon  by  thinner,  and  more 
distally  by  thicker  strands,  and  also  to  each  other  on  the 
dorsum  of  the  middle  phalanx.  They  finally  converge,  to  be 
attached  to  the  proximal  portion  of  the  terminal  phalanx. 
If  we  carefully  examine  a  dissection  of  the  dorsum  of  the 
hand  and  fingers  in  which  the  joints  are  lax,  fully  extend 


Fig.  57. — Position  for  immediate  rest  in  musculo- spiral  paralysis. 


::: 


MUSCULO-SPIRAL    PARALYSIS  117 

the  fingers  and  then,  still  keeping  the  metacarpophalangeal 
joint  over-extended,  flex  at  the  interphalangeal  joints,  the 
result  is  to  elongate,  not  the  communis  tendon,  but  the 
tendons  laterally  from  the  interossei.  If  we  bend  the  meta- 
carpophalangeal joint  we  immediately  elongate  the  com- 
munis tendons. 

Anatomical  Rest  in  Musculo-spiral  Paralysis 

(1)  The  triceps  not  only  arises  by  two  heads,  the  lateral 
ind  medial,  from  the  outer  border  and  dorsal  surface  of  the 
humerus,  but  also  by  the  long  or  scapula  head  which  is 
traced  to  the  rough  triangular  surface  of  the  scapula  im- 
mediately below  the  glenoid  fossa.  Hence,  to  rest  most 
effectively  our  triceps  it  is  not  only  necessary  to  extend  the 
elbow  joint  so  as  to  elongate  the  opposing  brachialis,  but 
also  to  elevate  the  arm  so  as  to  take  the  strain  of  the  weight 
of  the  limb  off  the  long  head. 

(2)  The  forearm  is  placed  in  the  mid  position  between 
pronation  and  supination,  or,  better,  in  the  slightly  supinated 
position,  and  the  wrist  is  hyper-extended  (dorsi-flexed)  so  as 
to  take  all  strain  off  the  supinator  brevis  and  the  extensors 
of  the  wrist.  In  this  way  we  antagonize  the  actions  of  the 
flexor  carpi  ulnaris,  flexor  carpi  radialis,  and  pronators. 
Full  supination  in  this  position  could  not  be  borne  by  the 
patient. 

(3)  The  thumb  is  extended  and  held  forcibly  abducted  by 
means  of  adhesive  plaster.  Too  much  attention  cannot  be 
paid  to  adequate  rest  of  the  long  abductor  of  the  thumb — 
the  extensor  ossis  metacarpi  pollicis. 

(4)  The  fingers  are  best  extended  at  the  outset,  not  only 
at  the  metacarpo-phalangeal  articulations,  but  at  the  inter- 
phalangeal joints  as  well.  In  this  way  the  lumbricales,  the 
opponents  of  the  extensor  communis,  are  relaxed  and 
elongated.  Although  communis  power  terminates  at  the 
proximal  phalanx,  nevertheless,  as  a  result  of  the  connection 
of  their  tendons  on  the  dorsum  of  this  phalanx  with  the 
interossei  tendons,  adequate  rest  is  not  secured  unless  the 
interossei  are  rested  as  well,  i.e.  unless  the  interphalangeal 


n8  THE    ACTION    OF    MUSCLES 

joints  are  extended.  Only  in  this  way  is  the  greatest  re- 
sistance offered  to  the  most  effective  factor  in  preventing 
recovery  in  a  case  of  musculo-spiral  paralysis,  namely  active 
contraction  of  the  flexors  of  the  fingers  and  wrist.  The 
greater  size  of  the  medial  or  inner  condyle  of  the  humerus 
gives  us  an  indication  of  the  relative  power  of  the  two  groups. 
These  positions  can  be  effected  by  means  of  the  abduction 
upper  limb  splint,  with  the  hand-piece  dorsi-flexed  and 
slightly  supinated.  They  are  admittedly  not  positions  of 
comfort,  but  after  an  operation  on  the  musculo-spiral  nerve 
or  at  the  onset  of  paralysis  they  are  those  which  give  most 
complete  rest.  Furthermore,  in  severe  old  flexor  contractions 
(which  it  may  be  stated  should  never  occur),  these  are  the 
positions  in  which  the  greatest  tension  and  stretching  force 
is  placed  on  the  tightened  tendons.  In  the  absence  of 
triceps  affection  and  when  the  flexion  contraction  is  not 
severe  a  "  long  cock-up  "  metal  or  aluminium  splint  may  be 
used.  This  is  bent  at  the  wrist  to  give  the  necessary  dorsi- 
flexion,  and  on  it  the  front  of  the  forearm  and  hand  rest. 

In  the  absence  of  contracture  of  the  flexors,  and  with 
commencing  recovery  of  the  common  extensor  this  splint 
need  only  extend  to  the  distal  portion  of  the  proximal 
phalanges,  leaving  the  middle  and  distal  phalanges  free. 
In  cases  where  the  extensor  tendons  of  the  wrist  only 
are  affected,  the  "  cock-up  "  splint  may  only  extend  from 
the  middle  of  the  forearm  to  the  metacarpo-phalangeal 
joints.     Numerous   patterns   of   these   "  cock-up "    splints 


er-jff 


Fig.  58. — Resting  the  hand  in  paralysis  of  the 
wrist  extenders  (Thomas). 

are  in  use,  and  instead  of  being  made  of  metal  they  may  be 
made  of  plaster  moulded  to  whatever  position  in  which  it 
is  desired  to  place  the  hand.  All  are  modelled,  however, 
on  the  original  "  drop  wrist  "  metal  splint  (fig.  58)  designed 
many  years  ago  by  Mr.  H.  O.  Thomas. 


MUSCULO-SPIRAL    PARALYSIS  119 

Method  of  Re-education  in  Musculo-spiral  Paralysis 

It  is  presumed  at  the  outset  that  in  a  case  of  nerve 
injury  or  division  surgical  repair  has  been  effected.  The 
treatment  of  this  form  of  paralysis  is  practically  the  treat- 
ment of  "  dropped  wrist,"  in  which  we  include  the  thumb 
and  the  fingers  at  the  metacarpophalangeal  joints.  The 
basic  principles  for  the  treatment  of  this  condition  were 
first  enunciated  by  H.  O.  Thomas.  Instead  of  assuming 
that  the  condition  of  wrist  drop  was  permanent  and  irre- 
mediable, Thomas  argued  that  the  primary  cause  might 
have  been  temporary  in  its  effects  ;  and  that  elongated  but 
recovered  extensors  were  mechanically  prevented  from  acting 
owing  to  the  contraction  of  their  opponents.  The  extensors 
were  not  of  necessity  permanently  paralysed  and  stretched. 

For  purposes  of  prognosis  Thomas  used  the  following  test : 
"  If  the  patient  be  asked  to  try  and  perform  by  the  exercise 
of  the  will  only  greater  flexion  than  already  exists,  the  fingers 
flex  readily,  and  also  by  the  act  of  the  will  extend  forward 
again  to  the  position  of  previous  repose  ;  furthermore, 
while  the  wrist  is  firmly  flexed  by  supplemental  assistance, 
the  patient  can  by  the  exercise  of  his  will  within  a  small 
radius  rapidly  flex  and  extend  his  fingers."  In  treatment 
he  placed  the  hands  and  fingers  by  means  of  the  long  cock-up 
splint  in  the  position  of  extreme  extension,  "  so  as  to  allow 
the  muscular  tissue  of  the  extensors  of  the  wrist  and  fingers 
to  retract  from  the  overstrain  or  overdraw."  On  removal 
of  the  splint  by  the  surgeon  to  test  the  result ;  "  should  the 
patient  by  the  exercise  of  his  will  be  able  to  maintain  exten- 
sion the  surgeon  may  allow  the  limb  to  be  used,  discontinu- 
ing the  angular  extension  apparatus."  Thomas  recognized 
that  a  muscle,  though  weakened  in  action  or  "  paralysed," 
might  have  recovered  ;  but  it  was  prevented  from  acting 
simply  because  during  its  period  of  weakness  its  opponent 
had  shortened,  with  the  result  that  it  itself  was  held 
mechanically  elongated.  He  did  not  of  course  regard  this 
simple  treatment  as  universally  successful  in  all  cases  of 
dropped  wrist.     In  cases  of  division  of  the  musculo-spiral 


120 


THE    ACTION    OF    MUSCLES 


nerve  and  subsequent  repair,  or  in  cases  of  poliomyelitis,  rest 
in  the  dorsi-flexed  wrist  position  does  not  of  itself  effect 
recovery,  though  in  the  latter,  if  the  case  is  seen  early,  this 
may  be  all  that  is  necessary. 

If  we  place  the  patient's  wrist  and  hand  in  the  position 
of  extension  at  the  outset,  we  have  made  a  good  beginning 
on  the  road  to  recovery.  No  attempt  at  re-education 
should  be  commenced  till  we  are  assured  that  we  have 
overcome  "  flexor  "  contracture.  Weakened  muscles  must 
not  be  asked  to  commence  work  at  a  mechanical  disability. 
The  hundred  units  of  work,  or  maximum  recovery,  will 
have  been  attained  when  the  patient  can  not  only  extend 
at  the  wrist  and  metacarpo-phalangeal  joints  from  acute 
flexion  with  the  dorsum  of  the  hand  uppermost,  i.e.  in  the 
position  of  over-pronation  ;  but  can  also  similarly  abduct 
the  thumb  with  extended  phalanges. 

For  exercising,  the  patient  should  lie  on  the  back  with 
the  head  supported  by  a  pillow,  and  the  arm  with  the  elbow 
slightly  flexed  should  rest  on  a  firm  pillow  placed  parallel 
to  the  patient's  side.  A  sheet  of  cardboard  should  be 
placed  under  the  limb.  When  the  hand  is  taken  off  the 
splint  it  should  be  placed  in  the  position  of  over-supination 


Fig.  59 
(S,  fig.  59),  the  palm  of  the  hand  being  uppermost.  The 
thumb,  while  the  wrist  and  fingers  are  being  exercised, 
should  be  held  abducted  by  a  strip  of  adhesive  plaster. 
In  the  supinated  position  slight  flexion  of  the  wrist  and 
fingers  is  permitted  and  the  patient  asked  to  extend.     In 


Fig.  60. — Musculo-spiral  paralysis. 

The  patient  is  unable  to  extend  the  wrist  in  the  over- prona ted  position,  but  can  do 
this  when  the  hand  is  placed  midway  between  pronation  and  supinationi 


[121 


MUSCULO-SPIRAL    PARALYSIS  121 

this  position  we  obtain  the  benefit  of  gravitational  effect, 
and  with  flexion  at  the  wrist  and  metacarpo-phalangeal 
joints  leverage  action  of  the  weakened  extensors  is  im- 
proved, since  at  these  joints  artificial  pulleys  are  formed. 
This  is  similar  to  the  effect  of  extension  of  the  wrist  in  help- 
ing the  action  of  weak  long  and  short  flexors  of  the  fingers. 
The  flexion  is  gradually  increased  till  finally  the  patient  can 
extend  from  full  flexion.  This  would  constitute  recovery  in 
this  position.  The  amount  of  flexion  can  be  graduated  by 
means  of  an  aluminium  "  cock-up  "  splint.  Help  may  be 
given  to  the  tendons  by  grasping  the  forearm  of  the  patient 
above  the  wrist.  As  regards  the  thumb,  slight  adduction  is 
at  first  allowed  by  slacking  the  adhesive  plaster  and  the 
patient  is  encouraged  to  abduct.  Similarly  slight  flexion 
(gradually  increased)  is  permitted  at  the  metacarpo- 
phalangeal and  interphalangeal  joints  to  encourage  exten- 
sion, and  the  latter  may  be  assisted  by  compression  of  the 
proximal  phalanx  and  of  the  metacarpus.  In  some  cases 
it  may  be  found  advisable  to  prevent  flexion  at  the  inter- 
phalangeal joints  of  the  fingers  by  means  of  small  straight 
splints,  only  allowing  movement  at  the  metacarpo-phalan- 
geal joints. 

As  regards  extension  of  weakened  fingers,  whether  of  the 
interphalangeal  joints  (interossei)  or  metacarpo-phalangeal 
(extensor  communis),  it  is  important  to  remember  that  this 
is  aided  by  flexion  of  the  wrist,  whether  the  position  of  the 
forearm  be  that  of  pronation,  or  supination,  or  midway 
between  the  two.  The  position  of  extension  of  the  wrist 
favours  flexion  of  the  fingers.  Thus,  in  testing  for  recovery 
of  the  extensor  communis  or  interossei  the  wrist  should  be 
slightly  flexed,  and  the  forearm  placed  in  a  position  of  over- 
supination.  Increased  work,  is  given  by  gradually  further 
extending  at  the  wrist. 

The  hand  of  the  patient  is  allowed  gradually  to  approach 
fromW  and  D  to  the  mid  prone  and  supine  position  N  (fig.  59). 
Thus  at  W  a  similar  procedure  to  the  above  is  adopted, 
and  recovery  obtained  before  pronating  to  D,  and  similarly 
at  D  before  pronating  to  N.    The  arc  is  gradually  increased 


122 


THE    ACTION    OF    MUSCLES 


to  R  and  F,  till  finally  the  over-pronated  position  P  is 
reached,  the  patient  can  then  extend  both  wrist  and  digits 
with  the  dorsum  of  the  hand  uppermost  (fig.  60).  If  the 
patient  cannot  extend  the  wrist  in  the  mid  prone  and 
supine  position  N,  it  is  positively  certain  he  will  be  unable 
to  do  it  in  the  over-pronated  position  P.  In  cases  of 
musculo-spiral  paralysis  much  patience  and  continuous 
work  may  be  necessary  to  obtain  recovery.  When  it  is 
decided  to  commence  re-education,  twenty  minutes  at  least 


Fig.  61. — Re-education  of  the  triceps. 

four  times  a  day  should  be  devoted  by  the  attendant J:o  this 
procedure. 

Supinator  Brevis. — In  cases  where  this  muscle  is  affected, 
this  would  be  manifested  by  difficulty  in  supinating  in 
the  extended  elbow  position  as  compared  with  that  in  the 
position  of  flexed  elbow.  With  the  elbow  extended  and 
the  patient  lying  down  we  would  work  gradually  along  the 
arc  S  P  (fig.  59),  being  certain  we  could  supinate  along 
the  arc  D  S  before  we  attempted  from  N,  the  mid  prone 
and  supine  position.     We  have  reached  our  100  units  of 


MUSCULO-SPIRAL    PARALYSIS 


123 


work  or  maximum  effort  when  we  can  supinate  from  P,  the 
position  of  over-pronation. 

Triceps. — The  patient  should  be  lying  down  and  the  limb 
placed  on  a  pillow  and  cardboard  as  above  described  (fig.  61). 

A  C  B  (fig.  62)  represents  the  elbow  extended,  and  D  C 
the  forearm  at  a  right  angle.  With  the  elbow  flexed  to 
E  45  degrees  we  ask  the  patient  to  extend  along  the  arc  E  B. 
Then  along  the  arc  D  B  and  then  F  B.  Recovery  takes 
place  in  this  position  when  the  patient  extends  the  elbow 


Fig.  62 


from  the  position  of  acute  flexion.  Further  work  is  given 
to  the  triceps  by  removing  the  pillow,  and  with  the  patient 
still  recumbent  and  the  arm  resting  on  the  table  the  arc  of 
flexion  is  again  gradually  increased  till  the  patient  extends 
from  full  flexion.  Also  with  the  elbow  and  arm  raised,  first 
on  a  small  and  later  on  a  large  pillow,  and  the  forearm  and 
hand  dependent  towards  the  patient's  body,  the  triceps  is 
asked  to  extend  the  forearm  against  gravity.  This  is  the 
reverse  method  of  re-education  to  that  described  for  the 


124  THE    ACTION    OF    MUSCLES 

brachialis.  The  patient  is  then  gradually  elevated  by  means 
of  pillows  to  the  erect  position — the  same  positions  and 
methods  being  repeated — recovery  is  complete  when  the 
patient,  sitting  or  standing  up,  can  extend  the  elbow  from 
full  flexion,  controlling  it  at  any  angle  of  extension. 

Division  of  the  Lumbricales. — As  the  lumbricales  arethe 
physiological  antagonists  of  the  communis  muscle  the  ques- 
tion may  arise  whether  division  of  these  is  not  justifiable  in 
old  cases  with  flexor  contraction  which  are  not  responding 
to  treatment.  As  the  profundus  and  sublimis  tendons  are 
intact  and  would  permit  of  the  coarser  flexion  movements, 
the  loss  of  the  lumbricales  would  be  of  little  moment  com- 
pared with  the  recovery  of  the  dropped  fingers.  The  tendons 
of  the  lumbricales  can  be  picked  up  where  they  join  the 
tendinous  expansions  from  the  interossei,  about  i'5  cm. 
above  the  metacarpo-phalangeal  joints  in  an  adult  (fig.  56, 
p.  115).  A  vertical  incision  is  made  on  the  middle  of  the 
lateral  or  radial  surface  of  the  proximal  phalanx  of  each 
finger. 

The  Movements  of  the  Thumb  and  Fingers  in  Median, 
Ulnar,  and  Musculo-spiral  Paralysis 

Median  Nerve. — (1)  Inability  : 

(a)  Cannot  flex  the  second  phalanges  of  any  fingers  (flexor 
sublimis). 

(b)  Cannot  flex  the  third  or  distal  phalanges  of  the  index 
and  middle  fingers  (flexor  profundus). 

(c)  Cannot  flex  the  proximal  phalanges  of  the  index  and 
middle  fingers  (two  outer  lumbricales). 

(d)  Cannot  flex  the  thumb  (flexor  longus  and  flexor  brevis 
pollicis),  nor  oppose  the  thumb  to  the  fingers  (opponens 
pollicis). 

(2)  Ability  : 

(a)  Can  abduct  or  adduct  the  fingers  (interossei). 

(b)  Can  extend  all  the  fingers  at  all  the  joints  (interossei 
and  extensor  communis). 

(c)  Can  bend  the  ring  and  little  fingers  at  the  metacarpo- 


MUSCULO-SPIRAL    PARALYSIS  125 

phalangeal  articulation  (two  inner  lumbricales)  and  at  the 
distal  interphalangeal  joints  flexor  profundus. 

(d)  Can  extend  and  abduct  the  thumb  (extensor  brevis 
and  extensor  longus  pollicis  and  the  long  abductor  or 
extensor  ossis). 

(e)  Can  adduct  the  thumb  (adductor  pollicis). 
Ulnar  Nerve. — (1)  Inability.  : 

(a)  Cannot  flex  the  proximal  phalanges  (lumbricales)  or 
distal  phalanges  (flexor  profundus)  of  the  ring  and  little 
fingers. 

(b)  Cannot  abduct  or  adduct  the  fingers  (interossei). 

(c)  Cannot  extend  the  middle  and  distal  phalanges  of  any 
fingers  (interossei). 

(d)  Cannot  adduct  the  thumb  (adductor  pollicis). 
(2)  Ability  : 

(a)  Can  flex  all  the  phalanges  of  the  index  and  middle 
fingers  (flexor  sublimis,  flexor  profundus,  and  lumbricales). 

(b)  Can  flex  the  middle  phalanges  of  the  ring  and  little 
fingers  (flexor  sublimis). 

(c)  Can  extend  the  proximal  phalanges  of  all  the  fingers 
(extensor  communis). 

(d)  Can  oppose  the  thumb  to  the  fingers  and  also  flex 
and  extend  as  well  as  abduct  it  (flexores  longus  and  brevis 
pollicis,  extensores  longus  and  brevis  pollicis,  long  and  short 
abductor  pollicis,  and  opponens  pollicis). 

Musculo- Spiral  Nerve. — (1)  Inability  : 

(a)  Cannot  extend  the  phalanges  or  metacarpus  of  the 
thumb  (extensor  longus,  extensor  brevis,  and  extensor 
ossis  or  long  abductor). 

(b)  Cannot  extend  the  proximal  phalanges  of  any  fingers 
(extensor  communis). 

(2)  Ability  : 

(a)  Can  flex,  oppose,  and  adduct  the  thumb  (long  and 
short  flexors,  opponens,  and  adductor  pollicis). 

(b)  Can  abduct  and  adduct  the  fingers  (interossei). 

(c)  Can  flex  the  proximal  phalanges  of  all  the  fingers 
(lumbricales). 

(d)  Can  flex  and  extend  the  middle  and  distal  phalanges 


126  THE    ACTION    OF    MUSCLES 

of    all   the  fingers  (flexor  sublimis,  flexor  profundus,  and 
interossei). 

In  considering  the  movement  of  abduction  of  the  thumb, 
I  regard  the  extensor  ossis  or  long  abductor  (musculo-spiral 
nerve)  as  the  important  factor,  rather  than  the  short  ab- 
ductor pollicis  (median  nerve). 


CHAPTER    VII 

THE    MUSCLES    OF   THE    THIGH 

The  movements  of  the  thigh  bone  or  femur,  all  of  which 
are  performed  at  the  hip  joint,  are  : 

(i)  Flexion. 

(2)  Extension. 

(3)  Adduction     or    movement    inwards   towards   the 

opposite  thigh. 

(4)  Abduction  or  movement  outwards. 

(5)  External  rotation. 

(6)  Internal  rotation. 

The  muscles  performing  these  movements  arise  from 
the  pelvis,  except  the  psoas  which  arises  from  the  lumbar 
spine.  They  are  all  examples  of  the  third  order  of  levers, 
in  which  the  power  lies  between  the  weight  to  be  moved 
and  the  centre  of  motion  at  the  hip  joint  or  fulcrum. 

These  movements  are  performed  by  the  following  muscles  : 

Flexion  Extension 

Iliacus,  psoas  major  Gluteus  maximus 

A  dduction  A  bduction 

Adductor  magnus  Gluteus  medius  and  Tensor  fasciae 

Adductor  longus  femoris 

Adductor  brevis 
Pectineus 

Rotation  outwards  Rotation  inwards 

Pyriformis  Gluteus  minimus 

Gemelli 

Obturator  internus 

Obturator  externus 

Quadratus  femoris 

127 


128 


THE    ACTION    OF    MUSCLES 


There  are  two  principal  regions  where  these  muscles  are 
inserted,  namely  the  great  trochanter  and  the  lesser  tro- 
chanter. The  insertions  of  the  adductors  are  however 
traced  down  the  shaft  of  the  femur  along  the  linea  aspera. 
When  we  speak  of  thigh  movements  we  presume  of  course 
that  the  thigh  is  not  fixed  by  the  body  weight ;    in  other 


GLUTEUS    MAX: 
(HIP  EXTENDER) 


KNEE   FLEXOR 


SOAS  MAG: 
FLEXOR) 


QUADRICEPS 
EXT:  OF  KNEE 


EXTENDERS 
OF  ANKL.E 


FLEXORS 
OF  ANKLE 


Fig.  63. — The  right  lower  limb  supporting  the  trunk  in  the  erect  position 
owing  to  contraction  of  the  gluteus  maximus  and  the  quadriceps. 

words,  we  are  not  using  it  for  support ;  or,  rather,  that  it  is 
not  fixed  by  muscle  so  as  to  support  the  weight  of  the  body. 
The  muscles  which  act  on  the  free  thigh,  with  the  trunk 
of  the  body  fixed,  also  act  on  the  free  trunk  when  the  thigh 
is  fixed.  Thus,  according  to  the  free  or  fixed  condition  of 
the  thigh  do  we  designate  the  origin  and  insertion  of  the 


THE    MUSCLES    OF    THE   THIGH 


129 


muscles.  If  we  stand  on  the  right  lower  extremity  (fig.  63), 
which  we  are  enabled  to  do  by  extending  the  knee 
(quadriceps)  and  the  hip  joint  (gluteus  maximus),  we  can 
readily  flex  the  left  thigh  (ilio-psoas)  on  the  trunk  and 
extend  it  readily  also  (gluteus  maximus).  If  we  stand  on 
both  lower  limbs,  the  knees  being  extended  (quadriceps), 
we  can  bend  the  trunk  on  the  thighs  at  the  hip    joint 


PSOAS 


GLUTEUS   MAXIMUS 


GLUTEUS 
MAXIMUS 


Fig.  64. — Flexion  and  extension  of  the  trunk  on  the  thigh. 

(ilio-psoas),  as  in  stooping  to  pick  up  an  object  from  off 
the  ground,  and  extend  it  to  resume  the  erect  position 
(gluteus  maximus).  The  lower  limbs  then  become  fixed 
points  on  which  the  trunk  flexes  and  extends  (fig.  64). 
Although  the  knee  and  ankle,  like  the  hip,  bear  the  whole 
weight  of  the  trunk,  yet  no  joint  in  the  body  is  the  subject 
of  more  continuous  movement  than  the  hip  ;  apart  from  the 
fact  that  in  comparison  with  the  knee  and  ankle  it  allows 
movement  in  all  possible  directions. 

9 


130  THE    ACTION    OF    MUSCLES 

When  we  stand  on  our  lower  limbs,  although  the  body 
weight  is  transmitted  unfavourably,  the  share  taken  by 
each  femur  is  equal,  and  the  centre  of  gravity  falls  exactly 
in  the  middle  between  the  two  thighs.  But  if  we  abduct 
the  trunk  on  to  one  or  the  other  limb  the  body  weight  is 
not  transmitted  to  the  ground  through  the  neck,  or  weakest 
part  of  the  femur,  but  through  the  middle  of  the  bone,  which 
is  its  strongest  part.  The  obliquity  and  length  of  the  neck 
of  the  femur,  though  predisposing  to  fracture  and  so  con- 
stituting a  source  of  weakness,  nevertheless,  are  essential, 
since  it  is  necessary  that  the  femur  should  move  freely  in 
all  directions. 

The  lower  limbs  of  man  are  relatively  longer  and  larger 
than  those  of  any  other  member  of  the  mammalian  order. 
The  prominences  of  the  femur  are  more  marked,  the  neck 
more  oblique,  and  the  pelvis  is  wider.  These,  together  with 
the  great  development  of  the  buttock  and  back  muscles, 
especially  the  gluteus  maximus,  are  related  to  man's  erect 
posture,  and  admit  of  freedom  as  supporting  agents  of  the 
fore  limbs,  so  that  they  can  respond  readily  to  the  require- 
ments of  the  will. 

I.  Flexion  and  Extension 

Flexion  movement  at  the  hip  joint,  whether  of  the  thigh  on 
the  trunk  or  of  the  trunk  on  the  thigh,  is  performed  by  the 
iliacus  and  psoas  magnus  muscles. .  The  psoas  is  a  long  and 
powerful  fleshy  muscle  arising  within  the  abdomen  on  each 
side  from  the  lumbar  vertebrae.  It  is  traced  ventral  to  the 
sacro-iliac  articulation,  and  coming  into  relation  with  the 
iliacus  passes  with  it  beneath  Poupart's  (inguinal)  ligament, 
and  is  inserted  by  a  tendon  into  the  lesser  trochanter  of  the 
femur.  The  iliacus,  also  a  strong  fleshy  muscle,  arises  within 
the  pelvis  from  the  iliac  fossa  and  base  of  the  sacrum.  It 
is  traced  with  the  psoas  beneath  Poupart's  ligament  to 
be  inserted  partly  into  the  tendon  of  the  psoas,  partly  into 
the  lesser  trochanter,  and  partly  into  the  femur — for  about 
i  inch— immediately  below  the  trochanter.  The  two 
muscles   being   so   closely  related   and   having   a   similar 


Fig.  65. — The  dorsal  abdominal  wall  of  the  kangaroo. 
d,  Diaphragm,     e,  I^ast  dorsal  nerve,     a,  Aorta,     b,  Post  caval  vein,     p,  Psoas  minor. 
m,  Quadratus  lumborum.     r,  Psoas  major,     k,  Iliacus.     n,  Epi-pubic  bone,     f,  Pectineus. 
s,  Sartorius.     t,  Rectus  femoris. 


(13 1 


THE    MUSCLES    OF    THE    THIGH  131 

insertion  are  designated  ilio-psoas.  In  addition  to  the  power 
of  flexion  of  the  hip  outward  rotatory  powers  have  been 
ascribed  to  the  ilio-psoas.  It  is  a  pure  flexor,  however, 
as  we  can  bend  the  thigh  in  the  position  of  either  internal 
or  external  rotation.  If  the  ilio-psoas  were  an  external 
rotator,  then  to  allow  internal  rotation  it  would  have  to  be 
in  a  state  of  relaxation  and  bending  of  the  thigh  should  then 
be  impossible.  In  connection  with  the  development  of 
the  erect  attitude  as  exemplified  in  man  the  four  principal 
muscular  changes  to  be  noted  are  : 

(1)  Deltoid  development. 

(2)  Selection    and    enlargement   of   the   psoas    major 

and  the  diminution  in  size,  or  complete  disap- 
pearance of  the  psoas  minor. 

(3)  The  great  relative  size  of  the  gluteus  maximus. 

(4)  Functional,    not     structural,     increases     in     the 

quadriceps. 

In  the  case  of  the  kangaroo,  representing  an  experiment 
towards  the  erect  position  at  an  early  stage  of  mammalian 
development,  we  find  that  the  psoas  minor  is  the  great  psoas 
and  that  the  muscle  corresponding  to  the  psoas  major  of 
man  is  the  smaller.  The  psoas  minor  on  each  side  forms 
in  the  kangaroo  a  large  fleshy  mass  (fig.  65)  traceable  from 
the  lower  dorsal  and  lumbar  regions  to  the  tubercle  of  the 
pubis.  In  this  marsupial  the  "  erect  posture  "  is  not  formed 
by  a  trunk  resting  on  two  practically  vertical  stems.  The 
erect  position  is  maintained  by  means  of  a  long  foot  and  an 
enormous  tail  propping  up  the  trunk  behind — the  knee  and 
hip  joints  being  flexed.  It  is  an  erect  position  in  the  sitting 
posture — the  tail  in  the  kangaroo  corresponding  to  a  chair 
as  used  by  man  (fig.  66).  In  the  platypus  also,  represent- 
ing in  various  directions  the  lowest  form  of  mammalian 
life,  the  psoas  minor  is  a  relatively  large  muscle  in  relation 
with  the  thoracic  and  lumbar  vertebrae,  while  the  psoas 
major  is  comparatively  insignificant.  The  erect  position 
in  man  has  necessitated  powerful  muscles  for  support  about 
the  centre  of  motion  of  the  body,  which  is  at  the  hip  joint. 


132  THE    ACTION    OF    MUSCLES 

The  development  of  powerful  extension  function  (gluteus 
maximus)  has  called  into  being  powerful  flexion.  The 
psoas,  instead  of  being  a  pelvic  muscle,  has  as  it  were  incor- 
porated into  itself  the  belly  of  the  psoas  minor,  and  has 
become  an  abdominal  muscle,  thus  increasing  its  effective- 
ness as  a  bender.  There  is  no  muscle  in  the  body  whose 
action  is  of  more  diagnostic  significance  than  that  of  the 
psoas  magnus  of  man.  Flexion  of  the  thigh,  due  to  reflex 
contraction  of  the  ilio-psoas  with  relaxation  and  elongation 


Fig.  66. — The  erect  posture  of  the  kangaroo. 

of  the  gluteus  maximus,  is  associated  with  many  pathological 
conditions,  such  as  the  passage  of  a  stone  in  the  ureter, 
appendicitis,  and  inflamed  lymphatic  glands  in  children,  etc. 
The  great  value,  however,  of  psoas  contraction  as  a 
diagnostic  help  is  in  connection  with  disease  of  the  lumbar 
vertebrae  and  joints,  sacro-iliac  joint,  and  the  hip  joint, 
with  all  of  which  it  is  in  relation.  In  hip  joint  disease 
however,  limitation  to  elongation  of  the  psoas  is  associated 
with  limitation  of  movement  in  all  directions.  The  psoas, 
by  its  -  contraction,  acts  as  a  sentry  and  places  the  hip 
joint  in  the  position  of  greatest  relative  ease.  If  we 
forcibly  extend  the  hip  the  shortened  psoas  arches  the 
spine,  producing  lordosis  ;  and  if  we  flex  the  hip  we 
straighten    the    spine.     H.    O.    Thomas,    recognizing    this 


THE    MUSCLES    OF   THE   THIGH 


133 


factor,  rested  the  joint,  by  means  of  his  dorsal  hip  splint, 
in  the  flexed  position  assumed  by  the  joint  for  the  purpose 
of  decreasing  tension — the  deformity  was  then  gradually 
reduced  and  the  angle  of  the  splint  altered  as  the  joint 
recovered.  The  psoas  was  gradually  allowed  to  relax 
and  elongate,  and  the  gluteus  maximus  to  contract  and 
shorten.  The  method  of  forcible  reduction,  as  by  weight 
and  pulley,  is  antagonistic  to  the  principle  that  regards 
psoas  contraction  as  nature's  means  of  placing  the  joint 
in  a  state  of  physiological  rest. 

It  was  John  Bell's  opinion,  over  a  century  ago,  that  the 
pernicious  doctrine  of  forcibly  resisting  the  contractions  of 
the  muscles  gave  rise  to  those  torturing  machines  for  the 


Fig.  67. — Testing  for  psoas  irritation. 

treatment  of  conditions  about  the  hip  which  were  associated 
with  the  names  of  Gooch  and  Wathen.  If  we  place  a 
healthy  child  in  the  prone  position  and  grasp  the  extended 
knee  of  either  side  the  amount  of  extension  at  the  hip 
joint,  or  in  other  words,  of  relaxation  and  elongation  of 
the  psoas,  is  sufficient  to  allow  the  thigh  to  be  brought 
almost  to  a  right  angle  to  the  pelvis  (fig.  67A).  In  cases 
of  suspected  psoas  irritation  this  forms  a  very  delicate 
test.  On  the  normal  side  there  is  this  free  extension,  on 
the  abnormal  the  patient  will  limit  the  extensor  action 
of  the  gluteus  maximus,  which  necessitates  relaxation  and 
elongation  of  an  irritated  psoas,  and  will  simulate  exten- 
sion by  raising  the  pelvis  on  the  affected  side  (fig.  67B). 


134  THE    ACTION    OF    MUSCLES 

This  is  a  serviceable  test  in  cases  of  suspected  psoas 
abscess.  Opposing  the  ilio-psoas  we  have  the  powerful 
fleshy  Gluteus  Maximus.  This  arises  from  the  upper 
and  back  part  of  the  dorsum  ilii,  back  of  the  sacrum  and 
coccyx,  and  from  the  great  sacro-sciatic  ligament.  The 
fibres  pass  obliquely  downwards  and  outwards,  and  are 
inserted  by  a  somewhat  broad  and  flat  tendon  into  the 
fascia  lata  and  for  about  7  cm.  along  the  gluteal  ridge, 
between  the  great  trochanter  and  the  linea  aspera  on  the 
posterior  aspect  of  the  femur  (fig.  72,  p.  143).  This  muscle 
is  the  extender  at  the  hip  joint.  With  the  pelvis  fixed  and 
the  hip  flexed  it  extends  the  femur  so  as  to  bring  the  thigh 
in  a  line  with  the  body.  Further  extension  (dorsi-flexion)  is 
however  permitted,  as  is  seen  particularly  in  children  and 
in  dancers  who,  with  the  body  supported  on  one  lower  limb, 
are  able  to  touch  the  back  of  the  head  with  the  other  heel, 
the  action  of  the  gluteus  maximus  being  assisted  by  flexion 
at  the  knee  joint.  After  we  stoop  to  pick  up  an  object  the 
gluteus  maximus,  using  the  femur  as  a  fixed  point,  draws 
the  pelvis  backwards,  and  with  it  the  trunk,  thus  enabling 
the  body  to  assume  the  erect  posture.  Its  action  is  seen 
also  when  we  rise  from  the  sitting  to  the  erect  posture. 
When  we  sit  with  the  body  erect  we  rest  the  feet  on  the 
ground  and  the  knees  and  hips  are  flexed.  When  we  rise, 
we  extend  at  the  hip  by  the  gluteus  maximus,  and  at  the 
knee  by  the  extensor  quadriceps.  The  gluteus  maximus  is 
also  described  as  an  abductor  and  external  rotator,  but  this 
is  not  so.  We  can  extend  at  the  hip  in  either  the  positions 
of  adduction  or  of  internal  rotation  ;  and  if  the  gluteus 
maximus  were  an  abductor  or  outward  rotator,  then,  during 
adduction  or  internal  rotation,  it  would  be  relaxed,  and  so 
could  not  contract  to  extend.  The  relatively  great  size  of 
the  gluteus  maximus  is  essentially  a  characteristic  of  man 
and  a  necessity  of  the  erect  position.  Various  experiments 
have  been  made  by  nature  with  this  muscle  at  different 
stages  of  mammalian  development.  In  the  platypus 
(fig.  68)  the  fibres  of  its  large  fleshy  belly  converge  behind 
the  leg  between  the  biceps  cruris  and  spur,  and  twisting 


THE   MUSCLES    OF   THE   THIGH  135 

on  themselves  are  inserted  at  the  middle  of  the  tibia  below 
the  inner  hamstrings.  It  acts  as  a  bender  of  the  knee.  In 
the  kangaroo  the  insertion  has  retracted  to  the  thigh  and 


KNEE 


KNEE 


Fig.  68. — Dorsal  dissection  of  platypus  to  show  gluteus  maximus 
and  biceps  cruris. 

s,  Spurs,  in  which  duct  of  gland  terminates,  m,  Poison  gland,  h,  Part  of  gland  and 
duct  passing  behind  biceps,  e,  Erector  spinae.  r,  Meso-gluteus.  a,  Abdominal  muscles. 
T,  Part  of  tail,     d,  E)cto-gluteus  (maximus).     w,  Anterior  tibial  muscle,     b,  Biceps  femoris. 


its  narrow  tendon  is  traced  along  the   lower  third  of   the 
femur.     Though  it  acts  in  this  marsupial  as  a  hip  extender 


136  THE   ACTION    OF    MUSCLES 

it  does  not  present  the  relative  predominance  in  size  over 
the  meso-gluteus  which  we  meet  with  in  man  (fig.  69).  Even 
in  the  anthropoid  apes  the  development  of  the  outer  gluteus 
is  small  compared  with  that  of  man,  for  whilst  according  to 
Macalister  it  forms  19%  of  the  musculature  round  the  hip 
in  man,  it  forms  13%  in  the  gorilla,  12 '5%  in  the  chim- 
panzee, and  only  12%  in  the  orang.  The  femur  in  the 
anthropoid  is  always  at  an  angle  with  the  trunk.  It  never 
approaches  the  vertical  as  seen  in  man.  In  the  shuffling 
gait  of  the  chimpanzee  seen  in  any  menagerie,  the  ape 
prefers  to  balance  himself  by  the  use  of  the  long  fore  limbs 
in  preference  to  depending  solely  on  the  hip  and  knee 
muscles.  Of  all  the  anthropoids  the  gorilla  in  its  attitude 
most  nearly  approaches  the  erect  posture  of  man. 

II.    Adduction  and  Abduction 

The  three  adductors,  which  were  described  by  the  older 
anatomists  under  the  name  triceps  femoris,  represent  a 
strong  group  of  muscles  running  from  the  pelvis  (arising 
from  the  outer  surfaces  of  the  pubis  and  ischium  anterior 
to  the  centre  of  the  hip  joint)  downwards  and  outwards  to 
the  inner  side  of  the  thigh.  They  are  inserted  along  the 
linea  aspera  on  the  back  of  the  femur  and  extend  from 
the  lesser  trochanter  to  the  inner  condyle. 

The  Adductor  Longus  arises  from  the  os  pubis  at  the 
junction  of  the  crest  with  the  symphysis  by  a  narrow  tendon, 
which  in  a  case  of  division  is  exposed  one  inch  below  the 
bone,  and  is  the  most  superficial  of  the  three  adductors. 

The  Adductor  Brevis,  which  lies  behind  the  longus, 
arises  farther  out  from  the  mid  line,  from  the  body  and 
descending  ramus  of  the  pubis. 

The  Adductor  Magnus,  the  largest  of  the  three,  arises 
still  more  dorsally  from  the  rami  of  the  pubis  and  ischium, 
as  well  as  from  the  tuberosity  of  the  ischium. 

The  Longus  passes  downwards,  outwards,  and  backwards, 
forming  a  well-defined  fleshy  belly  ending  in  a  flat  tendon, 
which  is  inserted  into  the  middle  of  the  linea  aspera  on  the 
inner  lip  for  about  4  inches. 


THE    MUSCLES    OF   THE   THIGH 


137 


ft         3  S-2 


-t->  p 
*"  be 
I3 

•9 


w 


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«  8  a  .2 
Iftl 

1**11 


•s  1  w"  i 

cu  v  .«   5 

1111 

t/J  "tl  -P    <G 


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138 


THE    ACTION    OF    MUSCLES 


The  Brevis,  like  the  longus,  has  a  narrow  origin,  but 
expands  into  a  fleshy  belly  and  is  inserted  by  a  flat  tendon 
into  the  linea  aspera  behind  and  above  the  longus,  and 
reaching  as  high  almost  as  the  lesser  trochanter.  Its  fibres 
run  less  obliquely  than  the  longus,   since,   owing  to  the 


ANGLE 
OF  PUBES 


mm 

Bm     ADDUCTOR   MAGNUS 


ADDUCTOR  BREVIS 


ADDUCTOR   LONQUS 


ADDUCTOR  MAGNUS 


Fig.  70. — The  adductors  of  the  thigh. 

position  of  its  insertion  and  its  size,  it  passes  more  directly 
between  the  pelvis  and  the  thigh. 

The  Magnus,  which  lies  behind  the  longus  and  brevis,  is 
inserted  along  the  whole  length  of  the  linea  aspera,  extend- 
ing below  to  the  adductor  tubercle  on  the  internal  or 
medial  condyle.  The  upper  fibres  pass  almost  directly 
across  to  the  upper  part  of  the  linea  aspera  from  the  pelvis, 
while  the  lower  pass  obliquely  downwards  and  backwards, 


THE    MUSCLES    OF   THE   THIGH  139 

and  the  muscle  forms  what  is  practically  a  partition  between 
the  front  and  back  of  the  thigh. 

Pectineus. — This  arises  from  the  ilio-pectineal  line  and 
the  adjacent  outer  surface  of  the  os  pubis,  and  passes  out- 
wards, downwards,  and  backwards,  to  be  inserted  at  a 
rough  line  leading  from  the  lesser  trochanter  to  the  linea 
aspera. 

Both  the  adductor  longus  and  the  magnus  are  inserted  at 
a  distance  from  the  centre  of  motion  at  the  hip  joint,  but 
compared  with  the  other  muscles  acting  on  the  femur  the 
pull  of  the  adductors  is  more  at  a  right  angle  than  oblique. 
This  increases  their  power.  These  muscles,  when  the  pelvis 
is  fixed,  all  adduct  the  femur,  bringing  it  inwards  towards 
the  mid  line,  i.e.  towards  the  opposite  thigh.  In  riding 
these  muscles  bring  the  knees  of  the  horseman  against 
the  animal's  flanks.  With  the  thighs  fixed  they  are  impor- 
tant muscles  in  maintaining  the  equilibrium  of  the  erect 
posture,  preventing  the  trunk  being  abducted  to  one  or  the 
other  side.  In  standing  erect  we  have  our  thighs  moder- 
ately abducted,  the  base  between  the  anterior  extremity  of 
each  foot  being  about  twelve  inches.  That  would  repre- 
sent the  state  of  equilibrium  between  the  abductors  and 
adductors.  If  we  stand  on  the  right  foot  only,  that  neces- 
sarily means  an  abduction  of  the  trunk  on  the  right  thigh, 
since  the  body  weight  is  transferred  through  that  femur  to 
the  ground.  The  adductores  of  that  side  have  relaxed  and 
the  abductor,  the  gluteus  medius,  has  contracted.  These 
states  can  be  increased  by  throwing  the  trunk  more  to  the 
right  side.  As  the  body  weight  is  taken  off  the  left  limb 
the  movements  on  the  left  side  are  abduction  or  adduction 
of  the  thigh  on  the  trunk  according  to  will. 

External  rotatory  and  other  powers  have  been  also 
ascribed  to  the  adductores.  Their  action  is  solely  to 
draw  the  thigh  inwards.  This  can  be  done  with  the  thigh 
in  the  position  either  of  flexion  or  extension  or  of  inward 
or  outward  rotation.  If  these  muscles  were  outward 
rotators  also,  then,  if  we  internally  rotated  the  thigh, 
they   should    be   in   a   physiological   state   of    relaxation. 


140  THE    ACTION    OF    MUSCLES 

Yet  in  this  state  they  can  also  contract,  since  we  can 
adduct  readily  the  abducted  and  internally  rotated  thigh. 
In  spastic  diseases  seen  in  children,  spasmodic  contraction 
of  the  adductors  forms  a  great  barrier  to  walking,  the 
knees  approach  each  other  and  even  cross,  and  there 
is  no  base  or  interval  between  the  feet  necessary  for  the 
maintenance  of  the  erect  posture.  Whether  the  primary 
trouble  is  associated  with  the  contracted  adductors,  or 
with  the  controlling  antagonistic  abductor  is  difficult  to 
state.  In  standing  erect  it  is  essential  for  equilibrium  that 
the  vertical  from  the  centre  of  gravity,  which  is  situated  at 
the  spinal  column  about  the  lumbo-sacral  region,  should  fall 
within  the  base  of  support,  i.e.  between  the  two  feet,  which 
in  ordinary  standing  are  usually  separated  anteriorly  by 
about  12  inches.  With  adduction  of  the  thigh  the  feet  are 
approximated  to  one  another  and  the  supporting  base 
lessened,  with  the  result  that  the  slightest  movement  to 
one  side  or  the  other  will  throw  the  vertical  outside  of  the 
base.  Various  measures  have  been  adopted  to  overcome 
this  when  it  is  permanent,  such  as  removing  a  wedge  from 
the  adductors,  etc.  As  a  rule  division  of  the  tendon  of  origin 
of  the  adductor  longus  and  of  the  middle  of  the  fleshy 


vr 

Fig.  71. — A  simple  abduction  or  adduction  frame. 
t,  Upper  thigh  wing,     k,  Knee  wing.     A,  Ankle  wing. 

gracilis,  which  is  associated  with  flexion  of  the  knee,  is 
sufficient  in  the  absence  of  feet  deformities — the  patient 
being  placed  with  the  thigh  forcibly  abducted  on  the  simple 
abduction  frame  shown  in  fig.  71.     It  is  worthy  of  note 


THE    MUSCLES    OF    THE    THIGH  141 

that  in  a  dissection  of  the  ventral  surface  of  the  thigh  in 
the  platypus  the  gracilis  is  seen  to  be  a  broad  fleshy  muscle 
covering  the  adductores,  semi-tendinosus,  and  semi-mem- 
branosus. 

Abduction. — The  antagonist  to  the  adductores  is  the 
Gluteus  Medius  which  abducts  or  draws  the  thigh  outwards 
when  the  pelvis  is  fixed,  or  abducts  the  trunk  when  the 
thigh  is  fixed.  In  walking,  when  we  stand  on  our  right 
limb  so  as  to  allow  the  left  limb  to  make  a  step,  we  abduct 
the  trunk  on  the  right  thigh  so  that  the  weight  of  the  body 
is  transmitted  through  the  right  femur  to  the  ground. 
This  fan-shaped  broad  and  fleshy  muscle,  the  posterior 
third  of  which  is  covered  by  the  gluteus  maximus,  arises 
from  the  outer  surface  of  the  pelvis,  from  that  portion 
of  the  outer  surface  of  the  ilium  between  the  upper  curved 
line  and  iliac  crest  above,  and  the  middle  curved  line  below. 
The  fibres  converge  to  the  great  trochanter,  where  they  are 
inserted  by  a  strong  flat  tendon  into  the  post-superior 
angle  and  the  outer  surface  (fig.  72).  The  length  of  the 
tendinous  insertion  of  the  gluteus  medius  is  about  3  inches. 
If  we  look  at  the  hip  joint  from  the  outer  side,  the  insertion 
of  this  muscle  is  immediately  above  the  trochanter,  and 
shortening  of  its  fibres  must  result  in  abduction  of  the  thigh. 
It  is  also  stated  by  some  authorities  to  have  powers  of 
extension  and  internal  rotation,  but  we  can  abduct  in  the 
position  of  either  flexion  or  of  external  rotation  of  the  hip. 
If  the  medius  were  an  extender  or  internal  rotator  it 
could  not  contract  so  as  to  abduct,  since  in  these  positions 
it  would  be  relaxed.  Compared  with  the  adductores  the 
gluteus  medius  has  its  insertion  only  a  short  distance  from 
the  centre  of  motion  in  the  hip  joint.  Though  having  a 
short  pull  this  is  direct,  and,  furthermore,  it  has  a  powerful 
muscular  belly. 

Assisting  the  gluteus  medius  in  its  action  as  an  abductor 
is  the  Tensor  Fasciae  Femoris.  This  takes  its  tendinous 
origin  from  the  fore  part  of  the  crested  ilium  for  about 
i-|-  inches.  It  passes  downwards  and  obliquely  backwards, 
and  becoming  thick  and  fleshy  about  the  middle  is  inserted 


142  THE    ACTION    OF    MUSCLES 

into  the  fascia  lata  on  the  outer  side  of  the  thigh  at  about 
the  junction  of  the  upper  and  middle  thirds.  As  this  muscle 
is  inserted  not  into  the  bone,  but  into  the  fascia  enveloping 
the  muscles  of  the  thigh,  its  use,  from  the  direction  of  the 
fibres  and  position  of  origin  and  insertion,  is  to  pull  the 
thigh  outwards  from  the  mid  line. 

III.    External  and  Internal  Rotation 

The  muscles  which  rotate  the  thigh  outwards  on  the 
trunk,  or  the  trunk  Outwards  on  the  thigh,  are  six  in  number, 
and,  coming  from  behind,  they  are  inserted  mainly  on  the 
inner  surface  of  the  great  trochanter  after  bending  round 
the  axis  of  the  femur. 

The  Pyrif  ormis  is  one  of  the  direct  muscular  connections 
between  the  axial  skeleton  and  the  lower  limb.  It  arises 
from  within  the  pelvis  from  the  front  of  the  sacrum,  emerges 
by  the  great  sacro-sciatic  foramen,  and  is  inserted  into  a 
facet  on  the  upper  and  inner  aspects  of  the  great  trochanter. 

The  Obturator  Internus  with  the  Superior  and  Inferior 
Gemellus  can,  from  the  point  of  view  of  insertion,  be  regarded 
as  one  muscle.  The  three  muscles  end  in  a  common  tendon 
which  is  inserted  to  a  facet  on  the  inner  surface  of  the  great 
trochanter  close  to  the  obturator  externus  and  below  the 
pyriformis.  The  superior  gemellus  arises  from  the  spine 
of  the  ischium  and  the  inferior  gemellus  from  the  ischial 
tuberosity.  The  obturator  internus  arises  from  within  the 
pelvis,  however,  from  the  inner  surface  of  the  outer  and 
front  wall  of  the  pelvis  around  the  inner  side  of  the  obturator 
foramen.  It  leaves  the  pelvis  through  the  lesser  sacro- 
sciatic  foramen,  the  margin  of  which  is  grooved,  cartilaginous, 
and  lined  with  a  synovial  bursa,  thus  forming  a  pulley  round 
which  the  tendon  plays,  by  which  means  the  leverage  is 
improved. 

The  Obturator  Externus. — This  triangular  muscle  covers 
the  outer  or  lateral  surface  of  the  front  wall  of  the  pelvis. 
It  arises  from  the  margins  of  the  obturator  or  thyroid 
foramen  formed  by  the  pubic  bone  and  ischium,  and  from 


THE    MUSCLES    OF    THE   THIGH 


143 


the  outer  surface  of  the  obturator  membrane,  and  passing 
backwards  and  out  on  the  dorsal  aspect  of  the  neck  of  the 
femur  is  inserted  by  a  strong  tendon  into  the  digital  fossa 
at  the  roof  of  the  great  trochanter.  It  is  a  short  muscle, 
and  is  broad  at  its  origin  but  narrow  at  its  insertion,  and 
twists  round  the  thigh  bone  between  it  and  the  pelvis. 


GLUTEUS  MED: 


GLUTEUS  MAX. 


PVR  I  FORM 


OBTUR:INT, 
&   GEMELU 


JSCH/AL   TUBER. 


GLUTEUS  MINI 


OBTUR:  EXT: 


V.]     GLUTEUS    MED: 

^        fAbductor) 

QT  TROC: 
I      QUADRATUS    FEM: 


GLUTEUS    MAX: 

lExtenaler) 


Fig.  72. — The  muscles  which  rotate  the  femur. 


The  Quadratus  Femoris  is  a  thin  muscle  measuring  about 
one  inch  from  its  upper  to  its  lower  border.  It  passes  from 
the  outer  border  of  the  tuberosity  of  the  ischium  to  be 
inserted  into  the  back  of  the  femur  between  the  .two  tuber- 
osities below  the  level  of  the  inter-trochanteric  line.  It  is 
interesting  to  note  that,  whilst  we  depend  on  a  single  muscle 
for  inward  rotation,  a  series  of  six  are  necessary  for  outward 


144  THE    ACTION    OF    MUSCLES 

rotation.  By  this  multiplicity  of  muscles,  flexion  and 
extension  are  unimpaired,  and  by  this  provision  accommo- 
dation is  found  for  the  numerous  muscular  insertions  which 
are  bunched  round  the  trochanters  so  as  to  allow  move- 
ment at  the  hip  joint  in  every  possible  direction. 

Internal  Rotation  is  performed  by  the  Gluteus  Minimus, 
which  is  the  physiological  antagonist  of  the  six  external 
rotators.  It  arises  from  the  outer  surface  of  the  ilium,  dorsal 
to  the  gluteus  medius,  between  the  middle  and  lower  curved 
lines,  and  in  front  extends  almost  as  far  forward  as  the 
crest  of  the  ilium,  and  behind  reaches  to  the  front  of  the 
great  sciatic  notch.  It  is  inserted  into  the  anterior  surface 
of  the  great  trochanter  (tig.  72).  The  length  of  the  insertion 
is  about  1  inch  and  width  about  \  inch.  The  tendon  of 
insertion,  which  is  about  1*5  inches  long,  describes  a  curve 
round  the  front  of  the  great  trochanter  and  lies  more  or 
less  parallel  with  the  neck  of  the  femur,  so  that  owing  to 
the  direction  of  its  pull  internal  rotation  will  be  produced. 

Rotatory  movements  are  the  most  limited  of  all  the 
motions  taking  place  at  the  hip  articulation.  In  standing, 
for  example,  on  the  left  lower  limb  with  the  right  free,  if  we 
keep  the  right  knee  extended  we  can  rotate  the  right  thigh 
inwards  or  outwards  on  the  fixed  trunk  with  ease.  As  we 
flex  the  thigh  this  becomes  more  difficult,  owing  to  the 
obliquity  of  the  axis  of  the  trunk  with  the  femur,  and  in 
the  position  of  acute  flexion  it  becomes  almost  impossible. 
This  applies  similarly  to  the  action  of  the  trunk  on  the 
thigh.  When  we  sit  on  a  chair  with  the  knees  and  hips 
flexed,  rotatory  movements  of  the  femur  are  practically 
impossible,  owing  to  the  angle  formed  by  the  axis  of  the  trunk 
with  the  thigh.  The  opposing  or  reciprocal  muscles  of 
rotation  can  be  regarded  as  being  in  a  state  of  equilibrium 
with  each  other.  Nor  can  we  roll  the  trunk  on  the  femur. 
Even  if  we  raise  the  right  foot  off  the  ground  we  cannot 
rotate  the  thigh  on  the  trunk,  but  if  we  extend  the  right 
knee,  which  is  associated  with  diminished  hip  flexion,  then 
rotation  can  be  effected  ;  and  this  is  especially  so  if  we  lean 
back  on  the  chair  so  as  to  render  the  thigh  and  trunk  level. 


CHAPTER    VIII 

MUSCLES    ACTING    ON    THE    LEG 

The  muscles  which  move  the  leg  are  divided  into  two 
groups,  benders  and  extenders.  The  centre  for  their 
motion  or  fulcrum  is  at  the  knee  joint,  and  they  are  all 
examples  of  levers  of  the  third  order,  in  which  the  power 
is  inserted  between  the  part  to  be  moved  and  the  fulcrum. 
In  all  cases  the  insertion  of  the  power  is  close  to  the  fulcrum. 

The  flexors  are  six  in  number,  five  having  an  inner  or 
medial  insertion  and  one  an  outer  or  lateral  insertion. 

The  inner  flexors  are  : 

Sartorius. 

Gracilis. 

Semi-tendinosus. 

Semi-membranosus. 

Popliteus. 

The  outer  one  is  : 

Biceps  cruris. 

The  popliteus,  though  part  of  its  insertion  is  seen  on  the 
inner  side  of  the  tibia,  passes  across  the  back  of  the  joint 
from  the  outer  to  the  inner  side. 

The  extensors  are  four  in  number  : 

Rectus. 

Vastus  externus 

Vastus   internum  |  Formin£  the  Quadriceps  Extensor. 

Crureus. 
io  145 


146  THE    ACTION    OF    MUSCLES 

I.    Flexors 

Sartorius. — This  is  the  longest  muscle  in  the  body  and 
crosses  the  front  of  the  thigh  obliquely  like  a  strap  from 
the  outer  to  the  inner  side.  Its  origin  is  from  the  pelvis 
in  the  region  of  the  anterior  superior  spine,  and  it  passes 
behind  the  inner  condyle  of  the  femur,  to  be  inserted  into 
the  upper  part  of  the  inner  surface  of  the  shaft  of  the  tibia. 
It  was  called  the  sartorius,  or  tailor's  muscle,  because  it 
was  supposed  to  abduct  the  thigh  enabling  one  leg  to  be 
crossed  over  the  other.     This  is  erroneous. 

The  squatting  position  assumed  by  tailors  depends  on 
flexion  of  the  knee  and  abduction  and  external  rotation  of 
the  thigh. 

Gracilis. — This  is  a  fleshy  narrow  muscle  placed  super- 
ficially on  the  inner  side  of  the  thigh.  It  arises  from  the 
descending  ramus  of  the  pubis  near  the  symphysis,  and  is 
inserted,  like  the  sartorius,  into  the  upper  part  of  the  inner 
surface  of  the  shaft  of  the  tibia  below  the  tuberosity.  In 
addition  to  its  power  as  a  flexor  of  the  knee  it  has  been 
described  as  an  adductor  of  the  tibia.  Both  the  sartorius 
and  gracilis  bend  the  leg  on  the  thigh  when  the  latter  is 
fixed.  They  arise  from  the  front  of  the  pelvis  at  either 
extremity  of  Poupart's  (inguinal)  ligament.  The  ham- 
strings arise  at  the  back  of  the  pelvis.  The  best  demon- 
stration of  flexor  action  is  seen  when  a  person  lies  on  the 
back  and,  with  the  knee  extended  and  leg  projecting  over 
the  end  of  a  table,  bends  the  extended  knee.  Also  when  the 
individual  lies  on  the  opposite  side,  for  example  the  left,  and 
with  the  right  knee  extended,  resting  against  the  left  knee, 
acutely  bends  the  right  one.  When  the  elbow  is  bent  the 
forearm  is  directed  to  the  front  of  the  body ;  in  the  case 
of  the  knee  the  leg  is  directed  towards  the  back.  When, 
with  the  body  lying  altogether  on  a  level  surface,  a  bed 
or  table,  we  flex  the  knee,  we  necessarily  flex  the  thigh 
as  well  at  the  hip,  otherwise  movement  could  not  occur. 
Flexion  of  the  hip  and  knee  are  not,  however,  necessarily 
accompaniments   of    each    other.     They   are    independent 


MUSCLES    ACTING    ON    THE    LEG  147 

movements.  Thus  the  individual,  when  lying  on  the  back 
in  bed,  can  acutely  flex  the  hip  with  the  knee  extended, 
and  then  flex  the  knee  with  ease. 

The  following  functions  are  also  ascribed  to  these 
muscles  : 

(1)  By  continuing  to  act  they  are  said  to  flex  the  thigh 
on  the  pelvis. 

(2)  Taking  their  fixed  point  from  below,  i.e.  with  the 
lower  extremities  steadied,  they  fix  the  pelvis  on  the  thigh, 
helping  to  maintain  the  body  erect,  and  may  further  flex 
the  pelvis  on  the  femur. 

(3)  Powers  of  abduction  and  external  rotation  of  the 
thigh  are  ascribed  during  flexion  to  the  sartorius,  and  of 
adduction  to  the  gracilis. 

These  muscles  are  not  attached  to  the  femur.  They  run 
between  the  pelvis  and  the  leg,  and  therefore  motion,  the 
result  of  their  action,  takes  place  at  the  knee,  not  at  the 
hip.  The  fulcrum  or  centre  for  action  is  not  the  hip  joint, 
but  the  knee  joint.  They  do  not  bend  at  the  hip  joint, 
and  they  can  act  as  flexors  of  the  knee  with  the  thighs 
extended.  Similarly  they  do  not  act  as  abductors,  adductors, 
or  thigh  rotators,  since  they  can  act  as  flexors  of- the  knee 
in  the  position  of  abduction,  adduction,  internal  or  external 
rotation  of  the  hip.  With  the  knee  extended,  rotatory 
powers  at  the  hip  joint  might  naturally  be  ascribed  to  these 
muscles ;  but  in  the  act  of  extension  at  the  knee  by  the 
quadriceps,  these  muscles  would  necessarily  relax  and 
elongate,  and  so  could  not  contract  and  shorten  in  order 
to  move  the  femur. 

As  regards  the  supposed  power  these  muscles  have  when, 
by  taking  their  fixed  point  from  below,  i.e.  with  fixation 
of  the  lower  extremities,  they  help  to  maintain  the  erect 
position  or  even  bend  the  trunk  on  the  femur,  we  again 
have  to  remark  that  the  fulcrum  for  their  action  is  not  at 
the  hip  but  at  the  knee.  These  muscles  do  not  bend  the 
trunk  at  the  hip,  or  act  as  supports  in  the  erect  position. 
Fixation  of  the  lower  extremities  to  allow  these  muscles  to 
take  their  fixed  point  from  below,  so  as  to  bend  the  trunk 


148  THE    ACTION    OF    MUSCLES 

at  the  hip,  necessitates  knee  extension.  To  allow  the 
quadriceps  to  extend  the  knee,  the  gracilis  and  sartorius  as 
flexors  would  of  necessity  be  relaxed  and  elongated,  and  so 
could  not  contract  to  produce  further  action  at  the  pelvis. 
In  spastic  paraplegia  of  children,  in  which  adduction  of 
the  thigh  is  a  marked  feature,  the  gracilis  is  contracted  and 
shortened  as  well  as  the  adductors  of  the  thigh.  But  its 
contraction  is  associated  with  accompanying  knee  flexion, 
of  which  it  is  the  main  cause,  and  not  with  adduction. 

Semi-tendinosus. — This  muscle  was  so  named  owing  to 
the  great  length  of  its  tendon  of  insertion,  which  usually 
begins  about  5  inches  above  the  knee  joint.  It  arises,  like 
the  long  head  of  the  biceps  cruris  and  the  semi-membranosus, 
from  the  back  of  the  tuberosity  of  the  ischium.  It  lies  on 
the  inner  and  back  of  the  thigh,  and  is  inserted,  like  the 
sartorius  and  gracilis,  into  the  upper  part  of  the  inner 
surface  of  the  shaft  of  the  tibia  just  below  the  inner  tuber- 
osity. These  three  insertions  lie  close  to  one  another, 
being  more  or  less  united  and  almost  implanted  like  one 
muscle  tendon. 

Semi-membranosus. — This  lies,  like  the  semi-tendinosus, 
on  the  inner  and  back  of  the  thigh,  and  like  it  also  arises  from 
the  back  of  the  tuberosity  of  the  ischium.  It  received  its 
name  from  the  fact  that  it  begins  and  ends  in  a  flattened 
somewhat  membranous-like  tendon.  It  is  inserted  more 
proximal  than  the  three  preceding  muscles,  into  the  back 
of  the  inner  tuberosity  or  condyle  of  the  tibia  above  that 
of  the  popliteus. 

Biceps  Cruris. — This  is  the  single  bender  inserted  on  the 
outside,  and  runs  from  the  pelvis  to  below  the  knee.  It  has 
two  heads  of  origin,  a  long  and  short.  The  long  head 
arises,  like  the  semi-tendinosus  and  semi-membranosus,  from 
the  back  part  of  the  tuberosity  of  the  ischium.  The  short 
head  arises  from  the  outer  lip  of  the  linea  aspera  on  the 
back  of  the  shaft  of  the  femur. 

This  short  head  begins  about  the  junction  of  the  upper 
and  middle  thirds  of  the  femur.  The  common  tendon  of 
insertion  is  into  the  outer  side  of  the  head  of  the  fibula, 


MUSCLES    ACTING    ON    THE    LEG  149 

and  by  a  fibrous  extension  to  the  outer  tuberosity  or  condyle 
of  the  tibia,  and  sometimes  into  the  outer  side  of  the  leg 
as  well.  The  "  hamstrings "  is  the  term  applied  to  the 
three  flexors  placed  on  the  back  of  the  thigh,  namely, 
biceps,  semi-tendinosus,  and  semi-membranosus. 

Popliteus. — This  muscle  and  the  short  head  of  the  biceps 
are  the  only  knee  flexors  not  connected  with  the  pelvis. 
It  is  a  triangular  muscle  lying  at  the  back  of  the  knee  joint, 
taking  its  origin  from  the  outer  aspect  of  the  outer  condyle 
of  the  femur  and,  crossing  the  joint,  passes  obliquely  down- 
wards and  inwards,  and  is  inserted  into  the  dorsal  surface  of 
the  upper  part  of  the  shaft  of  the  tibia  above  the  oblique  line. 

The  Hamstrings,  like  the  sartorius  and  gracilis,  taking 
their  fixed  position  at  the  pelvis,  flex  the  knee.  The 
popliteus,  taking  its  origin  from  the  fixed  femur,  also  flexes 
the  tibia.  As  to  the  action  of  the  hamstrings  when  the 
fixed  point  is  at  the  leg  much  confusion  seems  to  have 
arisen.  They  have  been  described  as  taking  a  very  impor- 
tant part  in  maintaining  the  body  erect.  For  example,  it 
is  stated  that  "  if  we  stand  erect  and  bend  the  body  for- 
wards at  the  hip  joint,  on  feeling  the  hamstrings  it  will  be 
found  that  they  are  in  strong  action  to  prevent  the  trunk 
from  falling  forwards,  and  are  the  chief  factors  concerned 
in  bringing  the  body  back  again  to  the  erect  position." 
When  we  stand  erect  our  knees  are  extended  owing  to 
quadriceps  contraction,  which  necessitates  a  state  of  re- 
laxation and  elongation  in  the  opposing  flexors. 

When  we  bend  the  body  forwards  at  the  hip  joint  in 
the  erect  position,  this  is  due  to  the  action  of  the  ilio-psoas 
taking  its  fixed  point  from  the  thigh,  and  is  permitted  owing 
to  associated  relaxation  and  elongation  of  its  opponent  the 
gluteus  maximus  (fix.  64,  p.  129).  The  body  is  brought  back 
to  the  erect  position  by  the  contraction  of  the  gluteus 
maximus,  and  the  relaxation  and  elongation  of  the  ilio- 
psoas. The  hamstrings  feel  tight,  not  owing  to  the  action 
of  contraction  and  shortening,  but  to  that  of  elonga- 
tion. This  is  accentuated  by  the  necessity,  further- 
more, of  accommodating  themselves  during  flexion  of  the 


150  THE    ACTION    OF    MUSCLES 

trunk  to  the  altered  state  of  the  hip  joint  over  which 
they  pass.  Taking  their  fixed  point  below,  their  action 
is  to  bend  the  trunk  and  thigh  on  the  leg  at  the  knee 
joint,  and  this  can  be  associated  with  either  flexion  or 
extension  at  the  hip.  Thus  it  is  possible  to  bend  the  rigid 
trunk  and  thigh  back  at  the  knee  joints,  and  though 
the  ordinary  individual  can  do  this  only  slightly,  acrobats 
and  athletes  can  produce  a  marked  flexion  backwards. 
This  is  a  pure  action  of  the  knee  flexors — the  quadriceps 
being  relaxed  and  the  condition  of  the  hip  being  one  of 
extension  owing  to  the  contraction  of  the  gluteus  maximus 
and  the  relaxation  of  the  ilio-psoas — the  remaining  hip 
muscles  being  in  a  state  of  equilibrium. 

In  this  backward  action  of  the  flexors  we  see  the  import- 
ance of  the  direct  pull  of  the  popliteus,  for  the  reason  of 
the  retention  of  which  in  man  I  was  often  puzzled.     As  the 
extending  vasti  also  arise  from  the  femur  and  the  rectus 
from  the  pelvis  we  have  acting  on  the  knee  both  on    the 
front  and  back  of  the  thigh,  long  and  short  levers.     Taking 
their  fixed  point  below,  the  most  important  action  of  the 
knee  flexors  is  in  connection  with  the  apparently  simple 
phenomenon  of  sitting.     When  we  stand  erect  we  have 
extension  of  the  knee,  the  extensors  being  contracted  and 
the  flexors  relaxed  and  elongated.     When  we  sit  on  a  chair 
there  is  flexion  at  the  knee  and  hip  joints,  and  the  body  is 
supported  on  the  ischial  tuberosities  between  which  the 
vertical,  through  the  centre  of  gravity,  passes.     In  sitting 
down  the  legs  and  feet  are  fixed  points,   although    it  is 
interesting  to  note  that  when  sitting,  which  means  mechani- 
cal support,  we  can  flex  and  extend  the  leg  on  the  thigh. 
To   acquire  the   erect  position   again  we  must  have  the 
legs  and  feet  as  fixed  points,  just  as  when  we  sat  down. 
The  flexion  at  the  hip  joint  during  sitting  is  a  bending  of 
the  trunk  on   the  femur   by   the  ilio-psoas,   the  gluteus 
maximus  being  relaxed.     The  flexion  at  the  knee  is  a  flexion 
of  the  trunk  and  femur  on  the  leg  at  the  knee  joint,  owing 
to  contraction  of  the  flexors  of  the  knee,  and  relaxation  and 
elongation  of  the  quadriceps  extensor. 


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MUSCLES    ACTING    ON    THE    LEG  151 

The  alteration  of  angle  at  the  hip  joint,  of  the  trunk  on 
the  femur,  is  an  independent  action  to  that  at  the  knee.  The 
action  of  the  flexors  of  the  knee  with  the  fixed  point  below 
is  a  flexion  of  the  trunk  and  femur  at  the  knee,  irrespective 
of  the  angle  between  the  pelvis,  i.e.  trunk  and  the  femur 
at  the  hip. 

These  principles  are  ■  illustrated  in  the  accompanying 
diagrams  (fig.  73).  In  addition  to  their  actions  as  flexors 
of  the  knee  these  muscles  can  also  produce  a  limited  amount 
of  rotation  movement  at  the  knee.  This  can  only  occur 
during  the  action  of  flexion,  when  the  muscles  are  contracted, 
and  not  during  extension  of  the  knee,  when  they  are  relaxed 
and  elongated.  It  is  a  limited  rotation  either  in  or  out  of 
perhaps  not  more  than  10  degrees,  and  can  be  demonstrated 
during  flexion  of  the  knee  by  placing  a  finger  on  the  tubercle 
of  the  tibia.  The  chief  muscle  producing  inward  rotation 
is  the  popliteus,  which  corresponds  to  the  pronator  teres  of 
the  upper  limb,  and  it  is  assisted  by  the  gracilis,  sartorius, 
semi-tendinosus,  and  semi-membranosus. 

The  outward  rotator  is  the  biceps.  It  has  an  advantage  as 
an  antagonist,  in  that  its  short  head  arises  from  the  shaft 
of  the  femur.  It  has  to  be  borne  in  mind  that  in  chronic 
diseases  of  the  knee  joint,  with  backward  displacement,  there 
is  frequently  some  outward  rotation  at  the  joint  due  to  the 
action  of  the  biceps — a  point  worth  remembering  in  reduc- 
tion of  the  displacement. 

In  the  marsupials  the  semi-tendinosus  and  semi-membra- 
nosus have  a  much  lower  attachment  on  the  tibia  than  in 
man  (fig.  74),  and  their  strength  in  the  phyllophagous  and 
arboreal  koala  is  shown  in  the  development  of  a  bony 
eminence  on  the  tibial  shaft.  In  the  platypus  the  gracilis 
is  a  broad  fleshy  flexor  of  great  power  and  size,  and  beneath 
it  lie  the  semi-membranosus,  semi-tendinosus,  and  the 
adductores  (fig.  75). 

The  most  variable,  or  rather  adaptable,  of  the  flexors  would 
appear  to  be  the  sartorius  and  the  biceps.  In  reference 
to  the  retention  in  man  of  the  peculiarly  situated  sartorius 
as  a  flexor  we  must  remember  that  in  the  marsupial, — and 


152 


THE   ACTION    OF    MUSCLES 


this  can  be  well  demonstrated  in  the  kangaroo, — it  is  an 
extensor,  being  related  to  the  quadriceps  extensor  at  the 
inner  side  of  the  gristly  patella  (fig.  74).  Hence  the  advan- 
tage of  this  muscle  as  a  graft  in  cases  of  weakness  of  the 

A 


Fig.  74. — Dissection  of  inner  side  of  knee. 
Wombat  (Phascolomys  Mitchelli). 
a,  Sartorius.    r,  Rectus  femoris.     b,  Gracilis,     v,  Vastus  internus.     e,  Great  adductor. 
M,   Biceps  cruris,    d,   Semi-membranosus.     c,   Semi-tendinosus,   with  biceps  attachment. 
H,  Gastrocnemius,     k,  Tibialis  posticus  and  deep  flexor. 

quadriceps.  The  biceps,  both  in  the  monotremes  and 
marsupials,  has  a  tendinous  attachment  along  the  whole 
length  of  the  leg,  and  this  is  particularly  well  shown  in  the 


MUSCLES   ACTING    ON    THE    LEG 


153 


koala  and  the  platypus  (fig.  68,  p.135).  Even  in  the  kangaroo 
with  its  attempt  at  the  erect  posture  this  feature  is  present 
(fig.  69,  p. 137).  It  is  interesting  to  note  that  in  the  gorilla,  the 
mammal  whose  attitude  nearly  approximates  to  the  erect 


Fig.  75. — Muscles  on  ventral  surface  of  thigh.     Platypus. 

h,  Sphincter,  k,  Iveft  Cowper's  gland,  w,  Portion  of  tail,  t,  Adductor  intertibialis. 
v,  Anterior  tibial  muscles,  m,  Sartorius.  a,  Gracilis  showing  extensive  insertion  on  leg. 
c,  Semi-tendinosus.     d,  Semi-metnbranosus.     b,  Adductores. 


posture  of  man,  the  portion  of  the  biceps  derived  from  the 
ischial  tuberosity  and  inserted  into  the  outer  tuberosity  of 
the  tibia  is  more  distinct  than  in  man,  from  that  portion 
having  its  origin  at  the  linea  aspera  of  the  femur,  which  is 
inserted  into  the  head  of  the  fibula. 


154  THE    ACTION    OF    MUSCLES 

II.     Extensors 

These  are  the  rectus  femoris,  two  vasti,  and  the  crureus, 
collectively  known  as  the  quadriceps  extensor. 

The  rectus  is  superficial,  lying  on  the  front  of  the  thigh 
with  the  vastus  internus  and  vastus  externus  on  either  side. 
The  crureus  lies  beneath  these,  being  extensively  related  to 
the  femur.  The  four  muscles  form  a  fleshy  mass  around 
the  fore  part  of  the  thigh. 

Rectus  Femoris. — This  muscle  has  a  double  head  or 
origin — one  head  arising  from  the  anterior  inferior  spine 
at  the  front  of  the  ilium,  and  the  other,  or  reflected  head, 
arises  from  the  dorsum  of  the  ilium  just  above  the  top  of 
the  acetabulum.  This  latter  is  demonstrated  by  the 
student  at  the  termination  of  the  gluteal  dissection.  These 
two  heads  form  a  single  tendon  about  4  inches  long.  This 
is  succeeded  by  the  fleshy  belly  of  the  muscle,  which,  as  it 
approaches  the  patella,  becomes  tendinous,  and  receiving 
laterally  portions  of  the  insertions  of  the  vasti  muscles  is 
inserted  with  the  tendon  of  the  crureus  into  the  upper 
border  of  the  patella.  In  the  muscle  belly  is  a  median 
tendinous  line,  towards  which  the  muscle  fibres  converge, 
giving  a  bipennate  arrangement  to  the  rectus.  This 
muscle  is  the  only  portion  of  the  quadriceps  arising  from  the 
pelvis  and  crossing  the  hip  joint. 

Vastus  Externus  or  Lateralis. — This  arises  from  the 
femur,  being  attached  to  the  lower  and  fore  part  of  the  great 
trochanter — to  the  rough  line  leading  from  the  trochanter 
to  the  linea  aspera — and  to  the  outer  lip -of  the  linea  aspera. 
The  muscular  belly  is  thick  and  fleshy,  and  the  membranous 
tendon  is  inserted  below  into  the  outer  margin  of  the  tendon 
of  the  rectus  and  the  upper  and  outer  border  of  the  patella. 

Vastus  Internus  or  Medialis. — This  is  not  so  large  nor 
fleshy  as  the  externus.  In  the  dissecting  room  it  is  almost 
impossible  to  separate  it  from  the  crureus,  the  line  of  union 
being  along  the  rounded  border  of  the  femur  between  the 
front  and  inner  surfaces.  It  arises  from  the  inner  lip  of 
the  linea  aspera  on  the  shaft  of  the  femur,  extending  from 


MUSCLES   ACTING    ON   THE    LEG  .        155 

the  anterior  line  between  the  two  trochanters  above  almost 
to  the  inner  condyle  below.  Its  strong  tendon  is  attached  to 
the  inner  border  of  the  rectus  tendon  and  to  the  upper  and 
inner  margin  of  the  patella.  It  is  interesting  to  note  that 
the  fleshy  fibres  of  the  internus  descend  lower  than  those  of 
the  externus,  and  some  are  even  inserted  directly  into  the 
patella.  This  muscular  extension  gives  rise  to  the  fleshy 
cushion  on  the  inside  of  the  thigh  above  the  knee. 

Crureus  (Vastus  Intermedius). — This  is  a  powerful 
muscle  having  a  fleshy  origin  from  the  upper  two-thirds  of 
the  shaft  of  the  femur  on  the  anterior  and  external  surfaces. 
Apart  from  its  close  connection  with  the  vastus  internus  it 
is  also  closely  related  to  the  vastus  externus  in  the  middle 
third  of  the  thigh.  Below,  it  is  joined  to  the  tendon  of  the 
rectus,  and  forms  the  deep  portion  of  the  quadriceps  ex- 
tensor tendon. 

Insertion  of  the  Quadriceps  Extensor. — The  tendon  of 
the  rectus,  expanding  at  its  termination,  is  joined  on  its 
under  surface  by  the  tendon  of  the  crureus  and  laterally 
by  those  of  the  vastus  externus  and  internus,  the  combined 
strong  tendon  being  attached  to  the  upper  part  and  sides 
of  the  patella  (fig.  76).  From  the  lower  border  of  the 
patella,  what  is  generally  regarded  as  the  real  tendon  of 
insertion  of  the  quadriceps  or  the  ligamentum  patellae  is  con- 
tinued over  the  front  of  the  knee  joint  and  is  inserted  into 
the  tubercle  of  the  tibia.  In  addition,  from  the  lower 
fibres  of  the  vastus  externus  and  internus  a  fibrous  sheet- 
like expansion  is  traced  not  only  to  the  capsule  of  the 
knee — the  so-called  lateral  patellar  ligaments — but  to  the 
inner  tuberosity  of  the  tibia  and  the  head  of  the  fibula  as 
well.  The  knee  joint  is  thus  protected  at  the  sides  as  well 
as  in  front. 

The  Patella  is  usually  regarded  as  a  large  sesamoid  bone 
whose  use  is  not  so  much  to  facilitate  the  movement  of  the 
extensor  tendon  over  the  condyles  of  the  femur,  since  for 
this  we  have  two  bursae — one  between  the  ligamentum  patellae 
and  the  tubercle  of  the  tibia,  and  the  other  between  the 
crureus  and  the  lower  part  of  the  femur — nor  to  protect 


156 


THE   ACTION    OF    MUSCLES 


the  joint,  which  is  an  important  service,  but  to  strengthen 
the  action  of  the  extensor  muscles.  It  is  worth  remembering 
however  that  the  patella  might  be  regarded  as  a  flexible 


RECTUS    F EM  ORIS 


VASTUS  INT 


CRUREUS 

VASTUS  EXT: 


CAPSULAR 
LIGAMENT 


PATELLA 


FIBROUS  EXTENSION 
TO    TIBIA 


FIBROUS    EXTENSION 
TO  FIBULA 


LIG.  PATELLAE 

Fig.  76. — Insertion  of  the  quadriceps  extensor. 

process  of  the  tibia  comparable  to  the  olecranon  of  the  ulna, 
the  two  being  connected  by  the  elastic  ligamentum  patellae. 
A  solid  inelastic  process  like  the  olecranon  would  however 
be  liable  to  direct  injury,  which  is  extremely  rare  in  the 
case  of  the  patella. 


MUSCLES    ACTING    ON    THE    LEG  157 

Against  this  view,  also,  is  the  fact  that  the  patella  is 
developed  as  a  separate  bone  in  both  monotremes  at  one 
end  of  the  mammalian  scale  and  in  man  at  the  other.  In 
the  mammalia  I  have  never  seen  a  patella  joined  normally 
to  the  tibia  like  the  olecranon  to  the  ulna,  nor  in  marsupials 
as  the  wombat,  where  no  patella  is  present,  is  there  a  process 
on  the  tibia  comparable  at  all  to  the  patella.  The  function 
of  the  patella  is  to  improve  leverage,  and  thus  to  increase 
the  power  of  the  quadriceps  extensor  muscle.  Its  function 
is  practically  that  of  a  pulley  gliding  on  the  smooth  surface 
of  the  lower  end  of  the  femur  between  the  two  condyles. 
By  its  means  the  motor  force  necessary  to  extend  the 
knee,  instead  of  acting  on  the  centre  motion  in  a 
straight  line  to  the  components  of  the  articulation,  acts 
at  an  angle,  and  consequently  its  range  of  power  is 
increased. 

The  patella  is  a  mechanical  aid  to  the  action  of  the 
quadriceps,  providing  as  it  were  a  new  base  for  extensor 
action,  since  it  lies  between  the  motor  forces  and  the  insertion 
of  their  tendon.  In  the  sitting  posture,  with  the  knees  bent, 
the  flexors  being  active  and  the  quadriceps  relaxed,  the 
patella  sinks  in  the  hollow  of  the  knee,  only  its  upper  third 
being  related  to  the  condyles  of  the  femur.  In  the  semi- 
flexed position,  when  the  quadriceps  acts,  the  patella  rises  out 
of  the  hollow,  and  becomes  more  prominent.  In  complete 
extension,  however,  it  is  right  at  the  summit  of  the  knee,  and 
only  the  lower  facets  are  related  to  the  articular  surfaces  of 
the  condyles.  In  a  case  seen  recently  of  a  soldier  whose 
left  patella  had  been  removed  some  months  previously  for 
compound  comminution,  it  was  interesting  to  note  that 
whilst  on  the  normal  right  side  the  patient  when  lying  on 
the  back  was  able  to  lift  the  heel  off  the  bed  with  the  knee 
fully  extended  ;  on  the  left  side  extension  of  the  knee  when 
the  heel  was  raised  was  incomplete,  being  accompanied  by 
a  flexion  of  about  15  degrees.  When  lying  on  the  right  side 
the  patient  could  elevate  the  left  heel  with  the  knee  straight, 
and  he  was  gradually  brought  from  that  position  to  the 
full  dorsal,  being  finally  able  to  raise  the  heel  with  the  knee 


158  THE    ACTION    OF    MUSCLES 

fully  extended.  Such  a  quadriceps,  though  at  a  mechanical 
disadvantage  compared  with  the  normal  is  sufficiently 
strong  to  enable  the  patient  to  walk.  When  walking  is 
commenced,  the  knee  should  be  at  first  extended,  as,  for 
example,  by  the  use  of  a  Thomas  caliper  splint.  By  means 
of  a  graduated  hinge  mechanism  opposite  the  knee  flexion 
can  be  increased — the  body  weight  being  thrown  gradually 
on  to  the  weakened  articulation. 

Functions  of  the  Quadriceps. — The  quadriceps  extends 
the  leg  on  the  thigh,  being  the  antagonist  of  the  six 
flexors.  Its  action  is  one  of  the  most  powerful  in  the  body. 
Part  of  the  muscle,  the  rectus,  arising  from  the  pelvis, 
passes  over  the  hip  and  knee,  the  remainder  pass  over  the 
knee  only.  Owing  to  the  pelvic  origin  of  the  rectus  this 
muscle  is  said  to  act  on  two  joints  at  the  same  time,  to 
bend  the  thigh  while  it  extends  the  knee,  and  reversely 
to  bend  the  trunk  on  the  thigh.  The  centre  of  motion  or 
fulcrum  for  quadriceps  action  is  not  the  hip,  but  the  knee 
joint.  Furthermore,  we  can  readily  extend  a  flexed  knee 
with  the  hip  extended,  and  can  bend  at  the  hip  with  the 
knee  flexed.  The  quadriceps  does  not  produce  flexion 
at  the  hip  joint,  that  action  is  solely  produced  by  the 
ilio-psoas. 

When  the  quadriceps  takes  its  fixed  point  from  below  its 
action  is  to  effect  extension  of  the  trunk  and  thigh  on  the 
leg  at  the  knee  joint ;  irrespective  of  alterations  of  the  angles 
of  flexion  of  the  components  at  the  hip  which  depend  on 
the  ilio-psoas  and  gluteus  maximus  muscles.  If,  with  the 
legs  and  feet  fixed,  we  bend  the  body  back  at  the  knee  the 
quadriceps  will  extend  the  body  again  to  the  erect  position. 
Similarly,  when  we  rise  from  the  sitting  posture,  although 
the  hip  alters  from  flexion  to  extension  owing  to  relaxation 
of  the  ilio-psoas  and  contraction  of  the  gluteus  maximus, 
it  is  the  quadriceps  which  is  the  factor  in  extending  the 
body  on  the  leg  at  the  knee  joint.  When  we  bend  the 
body  forward  at  the  hip  joint  in  standing,  to  pick  an  article 
off  the  ground,  this  action  is  produced  by  the  contraction 
of  the  ilio-psoas  and  the  relaxation  of  the  gluteus  maximus: 


MUSCLES    ACTING    ON    THE    LEG  159 

It  is  rendered  possible  owing  to  extension  at  the  knee 
by  the  contraction  of  the  quadriceps,  and  relaxation  and 
elongation  of  the  hamstrings  and  the  three  other  flexors. 

These  points  I  have  dealt  with  more  particularly  under 
the  actions  of  the  knee  flexors.  The  powerful  action  of 
the  quadriceps  in  producing  extension  at  the  knee  is  the 
basic  factor  in  the  maintenance  of  the  erect  position  of  man, 
not  only  in  standing  but  also  in  running  and  walking. 
The  continual  support  of  the  superincumbent  pressure  made 
by  the  whole  body  depends  on  the  quadricipes  extensores. 
In  their  action,  not  only  is  it  a  question  of  the  opposition 
of  the  flexors,  but  of  body  weight  and  gravity,  hence  their 
great  relative  size.  Two  centuries  ago  Cowper,  the  dis- 
tinguished British  anatomist,  weighed  the  extenders  and 
benders  of  the  knee,  and  found  that  the  extenders  greatly 
exceeded  the  benders  in  weight.  Thus  in  one  body  he 
found  the  extensors  weighed  3  lbs.  6  ozs.,  and  the  flexors 
1  lb.  7  ozs.  ;  and  in  another  the  extensors  weighed  4  lbs. 
8J-  ozs.,  and  the  flexors  2  lbs.  6  ozs. 

When  we  stand  erect  on  both  legs  each  quadriceps, 
though  contracted,  is  not  at  its  maximum  effort ;  and 
owing  to  the  fact  that  the  patella  appears  loose  some 
anatomists  have  stated  that  the  knee  extension  is  not 
dependent  on  muscular  aid.  The  knee  extension  does 
depend  on  quadriceps  contraction — the  position  of  the 
patella  tells  us  that.  A  child  whose  quadriceps  is  paralysed 
cannot  stand  if  the  knee  be  placed  in  the  position  of 
extension.  The  reserve  force  of  this  muscle  is  brought 
into  action  if  we  stand  on  one  limb,  when  the  quadriceps 
will  be  felt  further  to  contract  and  tighten.  The  strength 
of  the  quadriceps  is  also  shown  in  its  ability  to  produce  a 
fracture  of  the  patella.  This  not  infrequently  occurs  when 
a  person  is  going  upstairs.  The  balance  is  for  some  reason 
upset  while  the  knee  is  semi-flexed,  and  a  sudden  effort 
is  made  to  tighten  the  joint  in  extension.  The  result  is 
that  a  violent  spasm  of  the  quadriceps  occurs  which  is  not 
associated,  as  in  ordinary  circumstances,  with  a  pari  passu 
relaxation  and  elongation  of  the  flexors.     These  are  taken 


160  THE    ACTION    OF    MUSCLES 

unawares,  and  the  force  of  the  quadriceps  action  falls  on 
the  patella,  which  is  frequently  unable  to  bear  the  strain. 


Paralysis  of  the  Quadriceps  Extensor 

That  the  quadriceps  is  the  great  factor  in  maintaining 
the  erect  posture  is  well  illustrated  in  cases  of  infantile 
paralyses  affecting  the  lower  limb.  In  any  large  city 
numerous  cases  are  to  be  met  with,  ambulating  on  crutches 
with  a  dangling  limb,  unable  to  support  half  the  weight  of  the 
body  owing  to  a  paralysed  quadriceps  extensor  (fig.  81,  p.  166). 
Such  patients  may  be  able  however  to  stand  immediately 
if  the  knee  be  stiffened  by  means  of  a  splint  placed  behind 
the  knee  and  bandaged  to  the  limb ;  in  other  words,  by  the 
creation  artificially  of  a  contracted  quadriceps.  That  the 
term  "  quadriceps  extensor  "  has  a  different  value  in  man 
able  to  adopt  the  erect  attitude,  and  in  a  lower  mammal 
unable  to  stand  erect,  was  impressed  on  me  by  a  study  of 
cases  of  poliomyelitis.  Cases  of  quadriceps  "  paralysis  " 
were  met  with  in  this  disease  in  which  the  patient  was 
unable  to  stand,  or  when  lying  in  bed  to  raise  the  heel 
with  the  knee  extended.  When  he  lay,  however,  on  the 
side  opposite  to  that  which  was  affected  and  the  knee  was 
acutely  flexed,  the  leg  could  be  extended  with  ease. 

Because  the  patient  is  unable  to  raise  the  heel  off  the 
ground  with  the  knee  extended  when  sitting  on  a  chair — is 
unable,  that  is,  to  do  ioo  units  of  work  —  we  are  not 
justified  in  calling  the  quadriceps  "  paralysed."  On  the 
same  method  of  reasoning  the  quadriceps  tested  with  the 
patient  in  bed  and  with  the  knee  acutely  flexed  might  be 
regarded  as  normal,  since  it  can  perform  the  function  of  the 
quadriceps  as  given  in  text-books  ;  that  is  to  say,  exten- 
sion at  the  knee.  These  phenomena  admitted  of  only 
one  explanation — namely,  that  the  disease  was  revealing 
functional  stages  in  the  evolution  of  muscle.  They 
showed  clearly  that  muscle  action  was  a  complex  function — 
one  made  up  of  several  separate  activities — and  hence  the 
term  "  paralysis  of  muscles  "  is  really  referable  to  the  loss 


MUSCLES    ACTING    ON    THE    LEG  161 

of  some,  not  necessarily  all  of  the  functions.  The  recovery 
of  function,  like  the  loss,  follows  in  an  ancestral  or  evolu- 
tionary sequence.  This  applies  equally  to  the  deltoid  as 
to  the  quadriceps.  In  the  case  of  knee  extension  for  the 
erect  posture  new  muscles  have  not  been  called  into 
being — orthograde  functions  have  been  superimposed  on 
muscles  performing  in  other  mammals  plantigrade  motion. 

Charles  Bell  taught  us  that  the  anterior  cord  presides  over 
muscular  action,  and  Marshall  Hall  that  movement  can 
occur  reflexly  from  irritation  independently  of  volition.  A 
study,  however,  of  cases  of  infantile  paralysis  in  man,  re- 
garded as  the  most  advanced  mammalian  type,  demonstrates 
the  fact  also  that  the  anterior  cord  not  merely  presides  over 
"  muscular  action,"  but  recognizes  the  components  of  which 
that  function  is  made  up  ;  and  that  these  cell-controlled 
components  always  bear  a  definite  sequence  one  to  another. 
Though  similarly  placed  in  an  anatomical  sense  the  action 
of  the  quadriceps  is  vastly  different  in  platypus  and  in  man. 
The  quadriceps  in  platypus  responds  to  the  anatomical 
test  of  extension  of  a  flexed  knee,  but  that  is  a  different 
function  from  that  of  a  quadriceps,  which  will  allow  of  the 
orthograde  posture.  The  quadriceps  of  the  ape  has  a  more 
complex  function  than  that  of  the  platypus,  and  so,  similarly, 
has  man's  compared  with  the  anthropoid.  A  patient  who 
can  raise  the  heel  off  the  ground  when  sitting  with  the  knee 
extended  will  be  able  to  extend  the  acutely  flexed  knee 
in  bed  ;  but  the  patient  who  can  do  the  latter  need  not 
necessarily  be  able  to  do  the  former.  When,  therefore,  we 
are  told  that  the  quadriceps  is  paralysed  merely  because 
the  patient  is  unable  to  raise  the  heel  off  the  ground,  we 
are  told  something  which  is  biologically  untrue.  This  is 
a  question  apart  altogether  from  volition,  since  in  a  con- 
dition like  infantile  paralysis,  we  are  dealing  with  a  disease 
in  which  generally  cerebration  is  unaffected. 

A  study  of  the  anthropoids  at  any  menagerie  shows  the 
reluctance  with  which  the  fore  limb  is  dispensed  with  as  a 
means  of  support.  The  ape  prefers  the  knee  slightly  bent, 
with  the  balance  afforded  by  one  or  both  fore  limbs.     To 

II 


162  THE    ACTION    OF    MUSCLES 

assume  the  orthograde  posture  is  an  effort,  and  a  still 
greater  one  while  so  supported  to  raise  the  fore  limb  above 
the  head.  The  stiffening  of  the  knees  by  the  quadriceps 
which  has  enabled  man  to  stand  and  walk,  and  the  ability 
not  only  to  dispense  with  the  fore  limb  for  support,  but 
to  elevate  it  when  erect  above  the  head,  are  late  acquisitions 
in  man's  evolution,  and  are  hence  unstable. 

Method  of  Resting  a  Paralysed  Quadriceps  Extensor 

The  most  frequent  cause  of  this  condition  is  poliomyelitis 
in  children.  In  this  disease  it  is  essential  at  the  outset — 
even  if  only  one  limb  be  affected — to  rest  the  two,  as  pelvic 
tilting,  the  result  of  over-action  of  one  side,  easily  occurs, 
and  once  having  occurred  is  never  overcome.  It  is  also 
difficult  at  the  outset  to  make  sure  whether  the  abdominal 
muscles  are  affected,  and  furthermore,  only  in  this  way 
can  we  prevent  undue  rotation  of  the  hip,  and  abduction, 
or  adduction,  to  which  there  is  so  great  a  tendency.  Hence 
the  importance  of  noting  the  relationship  of  the  two  anterior 
superior  spines  to  the  umbilicus,  or  more  correctly  to  the 
mesial  plane.  The  spines  should  be  on  the  same  horizontal 
level.  This  can  be  immediately  effected  temporarily  by 
means  of  two  padded  boards  placed  behind  the  extended 
knee  from  the  upper  third  of  the  thigh  to  the  lower  third 
of  the  leg,  with  a  connecting  piece  across  the  middle — or  two 
long  back  splints  with  foot-pieces,  joined  together — and  per- 
manently effected  by  the  simple  abduction  splint  (fig.  71, 
p.  140).  The  quadriceps  is  in  a  position  of  anatomical  rest  be- 
cause its  opponents,  the  flexors,  are  in  a  position  of  relaxation 
and  elongation.  To  prevent  overstretching  of  the  flexors  a 
small  cushion  should  be  placed  under  the  knee.  With  the 
feet  elevated  on  a  pillow  strain  is  taken  off  the  ilio-psoas  and 
the  rectus  which  arises  from  the  pelvis.  Anatomically,  then, 
the  lower  limb,  like  the  upper,  can  be  easily  and  should  be 
immediately  rested.  If  these  details  are  attended  to  we 
have  gone  a  long  way  on  the  road  to  secure  a  recovery. 
Through   failure  to   effect  anatomical  rest  at   the  outset 


MUSCLES    ACTING    ON    THE    LEG 


163 


can  be  largely  ascribed  the  bad  results  met  with  in  in- 
fantile paralysis. 

Method  of  Re-education  for  a  Paralysed  Quadriceps 

A  paralysed  quadriceps  should  be  handled  with  the 
greatest  gentleness,  and  when  taken  off  the  splint  the  limb 
should  occupy  at  first  the  position  it  had  when  supported 


Fig.  77. — Complete  recovery  of  quadriceps  action  (maximum  work). 
An  erroneous  method  of  testing  for  paralysis. 


by  the  splint.  The  knee  should  not  be  bent  up  nor  allowed 
to  hang  over  the  edge  of  the  bed.  We  should  exercise  just 
as  much  care  as  in  the  case  of  a  fracture  of  the  femur.  It 
is  best  for  the  patient  to  rest  on  a  firm  bed,  so  that  move- 
ments can  be  carried  out  without  disturbance.  A  sheet 
of  cardboard  should  be  placed  under  the  limb  to  obviate 
all  resistances  to  movement.  The  maximum  work — 
namely,  100  units — is  represented  by  the  ability  to  stand 


164 


THE    ACTION    OF    MUSCLES 


erect  with  the  knees  straight,  or  to  raise  the  heel  off  the 
bed  when  lying  with  the  knee  extended,  and  similarly  when 


Fig.  78. — Commencing  re-education  of  the  quadriceps. 

sitting  on  a  chair  (fig.  77).  The  minimum  is  represented 
by  the  ability  to  straighten  the  knee  without  abduction, 
with  the  patient  on  the  back  and  the  knee  slightly  bent, 


MUSCLES    ACTING    ON    THE    LEG  165 

actively  or  passively.  On  flexing  the  leg,  for  example,  one 
inch,  it  may  be  noticed  that  the  limb  falls  straight ;  or,  if 
bent,  say  three  inches,  the  patient  may  be  unable  to  straighten 
the  knee,  but  can  prevent  the  limb  abducting  ;  that  can  be 
regarded  as  evidence  of  recovery.  The  flexion  is  gradually 
increased,  the  fall  becomes  gradually  replaced  by  a  definite 
push,  till  finally  the  patient  holding  the  knee  in  the  position 
of  acute  flexion,  without  abduction  or  adduction  of  the 
thigh,  is  able  to  straighten  the  limb.  It  may  be  necessary 
to  initiate  action  with  the  patient  lying  on  the  opposite 
side,  and  not  on  the  back,  beginning  the  push  with  a  two-inch 
flexion,  and  in  this  early  movement  hip  action  is  unhindered. 
An  early  sign  of  recovery  is  the  power  of  adduction  or 
abduction  of  the  whole  limb  when  on  the  back  with  the  knee 
straight,  especially  the  latter,  and  progress  can  be  stimu- 
lated by  bandaging  a  splint  to  the  back  of  the  knee. 

Our  next  endeavour  is  to  secure  extension  from  full 
flexion  when  lying  on  the  opposite  side,  with  the  thigh 
fixed  (fig.  78).  This  is  accomplished  by  beginning  with, 
say,  a  3-inch  flexion  and  gradually  increasing,  always  com- 
mencing each  day,  however,  at  the  3-inch  stage.  It  is 
wrong  practice  to  flex  the  knee  beyond  a  point  at  which 


QUADRICEPS 


Fig.  79. — Complete  recovery  of  quadriceps.     100  units  of  work, 
or  maximum. 

extension  effort  becomes  manifest.  The  action  is  aided  by 
allowing  the  patient  to  flex  and  extend  the  knee  when  on 
the  side,  but  with  the  thigh  free.  The  time  now  comes  when 
our  attention  is  directed  to  the  power  of  raising  the  heel 
off  the  bed  from  the  hip  with  the  knee  extended  (fig.  79). 
To  our  surprise  the  patient,  when  lying  on  the  sound  side, 
may   lift    the    affected  limb    in   one   piece    and   swing   it 


i66 


THE    ACTION    OF    MUSCLES 


forwards  and  backwards  with  ease.  This  is  an  action  of 
the  ilio-psoas  muscle,  aided  by  the  abductor  of  the  thigh, 
but  is  only  rendered  possible  by  the  action  of  the  quadriceps 
extensor  in  keeping  the  knee  stiff.     If  unable  to  do  this  we 


Fig.  80. — Almost  complete  recovery  of  quadriceps 
(same  patient  as  fig.  81). 

can  assist  the  patient  to  initiate  and  practise  the  movement 
with  the  knee  stiffened  by  a  cardboard  or  wooden  splint 
behind  the  joint — that  is  to  say,  we  produce  an  artificial 
quadriceps.  Objection  may  be  raised  that  the  elevation  of 
the  limb  in  one  piece  when  on  the  side  is  dependent  on 


Fig.  8i. — Contracted  knee  of  ten  years'  duration,  the  result  of  contrac- 
tion of  flexors  owing  to  paralysed  quadriceps  (same  case  as  fig.  80). 

the  stiffening  action  of  the  lateral  ligaments.  It  is,  however, 
a  distinctly  muscular  action,  and  ligaments  do  not  produce 
motion. 

This  can  be  proved  in  the  case  of  a  severe  quadriceps 
paralysis,  when  the  patient  with  a  sound  ilio-psoas  will  make 


MUSCLES    ACTING    ON    THE    LEG  167 

unsuccessful  efforts  to  raise  the  heel  when  on  the  side — the 
knee  remaining  bent ;  but  when  the  splint  is  applied 
behind  the  knee  will  lift  the  limb  with  ease.  Although  able 
to  raise  the  limb  in  one  piece  when  on  the  side,  yet  when 
turned  on  the  back,  this,  which  is  the  maximum  effort,  is 
impossible.  The  graduated  method  is  again  applied.  We 
gradually  alter  the  tilt  of  the  body  (fig.  80),  which  can  be 
done  by  means  of  a  pillow,  from  the  lateral  to  the  supine 
position,  till  finally  our  maximum  of  100  units  of  work  is 
reached.  If,  when  seen,  the  knee  has  been  bent  owing  to 
over-strong  hamstrings  (fig.  81),  it  should  first  be  gradually 
straightened  before  true  function  is  commenced.  There 
should  be  no  flexion  at  any  time  beyond  the  point  at  which 
extension  effort  has  become  manifest. 


CHAPTER    IX 

MUSCLES    ACTING    ON    THE    FOOT   (GREAT 
SCIATIC   NERVE) 

The  muscles  acting  on  the  foot  are  eight  in  number,  and 
produce  the  movements  of  flexion  or  upward  movement 
(dorsi-flexion),  and  extension  or  downward  movement 
(plantar  flexion)  ;  also  of  adduction,  inversion,  or  turning 
the  foot  in  ;  and  abduction,  eversion,  or  turning  the  foot 
out.  Flexion  and  extension  take  place  at  the  ankle  joint, 
and  inversion  and  eversion  chiefly  in  the  tarsal  articulations, 
and  more  particularly  in  the  mid-tarsal  joint.  The  muscles 
are : 

Flexion  Extension 

Tibialis  anticus  Gastrocnemius 

Peroneus  tertius  Soleus 

Peroneus  brevis  Plantaris 

Tibialis  posticus 
v        Peroneus  longus 

Inversion  Eversion 

Tibialis  anticus  with  flexion  Peroneus  longus  with  extension 

Tibialis  posticus  with  extension      Peroneus  brevis  with  flexion 

Peroneus  tertius  with  flexion 

FLEXION    AND    EXTENSION    OF    THE    FOOT 

I.  Flexion 

Tibialis  Anticus. — This  muscle  is  placed  on  the  outer 
side  of  the  tibia  arising  from  the  lateral  tuberosity  or  condyle 
and  upper  two  thirds  of  the  shaft  of  that  bone.  The  belly 
is  adherent  to  the  deep  fascia  covering  it,  and  terminates 
about  4  inches  above  the  ankle  in  a  tendon  which,  crossing 
the  ankle  joint,  is  inserted  on  the  inner  surface  of  the  first 

168 


MUSCLES    ACTING    ON    THE    FOOT         169 

or  internal  cuneiform  bone  and  on  the  base  of  the  meta- 
tarsal bone  of  the  great  toe.     Tendon  comprises  half  the 
length  of  this  muscle. 
Peroneus  Tertius. — This  is  usually  described  as  a  special- 


PERONEUS  BREWS 


peroneus  tertius 


TIBIAUS 
A  NT /C US 


Fig.  82. — The  benders  (dorsi- flexors)  of  the  foot. 

ized  portion  of  the  extensor  longus  digitorum,  not  specially 
innervated,  and  not  always  present.  When  present  it 
represents  the  outer  part  of  the  extensor  brevis  digitorum, 
retaining  its  old  mammalian  origin  from  the  leg,  although 
the  main  part  of  the  muscle  has  migrated  to  the  foot.     Its 


170  THE    ACTION    OF    MUSCLES 

tendon  passes  in  front  of  the  outer  malleolus,  while  those  of 
the  peroneus  longus  and  brevis  pass  behind. 

It  arises  from  the  lower  third  of  the  anterior  surfaces  of 
the  fibula,  and  its  tendon  is  inserted  into  the  dorsal  surface 
of  the  base  of  the  metatarsal  bone  of  the  little  toe.  There 
is  no  slip  in  the  fore  limb  corresponding  to  the  peroneus 
tertius,  and  this  muscle  was  regarded  by  Owen  and  others 
as  peculiar  to  the  human  leg.  In  the  leg  of  the  wombat, 
however,  there  is  a  well-defined  fleshy  muscle  corresponding 
to  the  peroneus  tertius,  and  having  an  insertion  on  the 
dorsum  of  the  foot  laterally.  This  sends  a  tendinous  slip 
to  extend  the  little  toe. 

Peroneus  Brevis. — This  arises  from  the  lower  two  thirds 
of  the  outer  surface  of  the  fibula,  and  an  important  point 
is  that  it  is  fleshy  lower  down  in  the  leg  than  the  longus. 
It  passes  with  the  peroneui  longus  behind  the  outer  malleolus 
which  forms  a  pulley  for  the  improvement  of  their  action, 
especially  of  the  longus,  and  its  tendon,  running  along  the 
outer  side  of  the  os  calcis,  is  inserted  into  the  tuberosity 
and  dorsal  surface  of  the  base  of  the  metatarsal  bone  of  the 
little  toe.  The  insertion  of  this  muscle  is  dorsal  and  not 
plantar.  It  is  always  demonstrated  in  dissections  of  the 
dorsal  aspect  and  not  in  those  of  the  sole  of  the  foot.  Ex- 
pansions from  the  tendon,  just  before  its  insertion,  I  have 
always  found  to  be  directed  towards  the  medial  aspect 
dorsally  and  not  towards  the  plantar  aspect.  This  point 
is  of  the  utmost  importance  in  a  consideration  of  the  action 
of  the  peronei. 

II,  Extension 

Gastrocnemius. — This  is  the  great  calf  muscle,  and  arises 
by  two  tendinous  heads — an  inner  and  an  outer.  The  outer 
head  arises  from  the  upper  and  back  of  the  lateral  or  outer 
condyle,  while  the  inner  or  larger  head  arises  just  above 
the  inner  or  medial  condyle,  between  it  and  the  adductor 
tubercle.  Each  tendon  is  connected  with  a  fleshy  belly, 
and  the  two  bellies  being  connected  firmly  about  the  middle 


MUSCLES    ACTING    ON    THE    FOOT  171 

of  the  leg  are  succeeded  by  a  large  flat  tendon,  broad  above 
and  narrowing  below — the  superficial  portion  of  the  tendo 
achillis — and  this  is  inserted  into  the  lower  part  of  the 
posterior  surface  of  the  calcaneus  or  os  calcis.  A  bursa  to 
facilitate  action  lies  beneath  the  tendon  at  its  insertion. 
This  muscle,  unlike  the  soleus,  crosses  the  knee  joint. 

Soleus. — This  lies  beneath  the  gastrocnemius,  and 
arises  by  two  heads  also,  one  from  the  head  of  the  fibula 
and  upper  third  of  the  back  of  that  bone,  and  the  other 
from  the  middle  third  of  the  inner  or  mesial  border  of  the 
tibia.  The  tibial  origin  would  appear  to  be  peculiar  to 
man.  Even  in  the  gorilla  the  soleus  has  an  origin  from  the 
fibula  only.  Some  fibres  also  arise  from  a  tendinous  arch 
between  the  two  heads.  The  fibula  head  is  large  and 
round  and  the  tibial  head  smaller  and  flatter.  They  are 
succeeded  by  a  fleshy  belly,  which  about  the  middle  of  the 
leg  is  succeeded  by  a  tendon,  and  this  blending  with  that 
of  the  gastrocnemius  forms  the  greater  part  of  the  tendo 
achillis.  This,  as  stated  above,  is  inserted  into  the  posterior 
or  dorsal  aspect  of  the  os  calcis.  As  the  powerful  tendo 
achillis  approaches  the  heel  it  narrows,  but  on  reaching  the 
bone  it  spreads  out  to  take  a  firm  grip.  This  muscle  does 
not  cross  the  knee  joint.  The  calcaneus  or  os  calcis  can  be 
regarded  as  a  point  of  support  for  the  whole  foot,  and 
through  it  is  exercised  the  lever  power  by  which  the  super- 
incumbent body  weight  is  raised  in  the  peculiar  bipedal 
walk  of  man.  Its  strength  and  backward  development  re- 
late purely  to  increase  of  power,  and  depend  on  muscular 
development.  There  is  a  distinct  difference  in  the  size  of 
the  os  calcis  in  African  races,  whose  members  walk  bare- 
footed and  carry  heavy  burdens,  and  the  modern  European. 
By  means  of  a  single  tendon  of  insertion  nature  is  able  to 
concentrate  all  the  force  of  the  powerful  calf  muscles  on 
the  calcaneus. 

Plantaris. — This  muscle  is  often  wanting.  It  is  so  called 
as  it  was  thought  it  was  continued  on  as  the  plantar  fascia. 
Comparative  studies  show  that  this  fascia  results  from  the 
retrogression  of  the  plantaris.     Its  slender  fleshy  belly  is 


172 


THE    ACTION    OF    MUSCLES 


about  three  inches  long,  and  is  traced  to  the  lateral  condyle 
of  the  femur.  Its  narrow  tendon  runs  along  the  inner  mar- 
gin of  the  tendo  achillis  to  the  posterior  surface  of  the  calca- 
neus. This  muscle  crosses  the  knee  joint.  It  has  never 
been  detected,  as  far  as  I  know,  in  the  gorilla. 

Tibialis  Posticus. — This  is  the  most  deeply  seated  muscle 
in  the  leg,  and  arises  below  the  knee  joint  from  both  the 


TIBIALIS 

POSTICUS 


PERONEUS   LONaUS 


TENDON   OF  ACH: 

Fig.  83. — The  extenders  (plantar-flexors)  of  the  foot. 


tibia  and  fibula,  as  well  as  from  the  interosseous  membrane 
between  the  bones,  and  from  the  deep  fascia  over  it.  Its 
attachment  to  the  back  of  the  fibula  is  from  the  upper 
two  thirds  of  the  inner  surface,  and  to  the  tibia  from  the 
dorsal  or  posterior  surface  below  the  oblique  line.  The 
muscle  belly  terminates  in  a  tendon,  and  this  passes  behind 
the  inner  malleolus,  which  acts  as  a  pulley  for  it  like  the 


MUSCLES    ACTING    ON    THE    FOOT  173 

outer  malleolus  does  for  the  peronei.  The  principal  insertion 
of  the  tendon  is  to  the  plantar  surface  of  the  tubercle  of  the 
navicular  or  scaphoid  and  the  adjacent  internal  cuneiform 
bones  ;  but,  in  addition,  fibrous  expansions  are  given  off  to 
the  two  outer  cuneiform  bones — cuboid  and  sustentaculum 
of  the  calcaneus — and  also  to  the  second,  third,  and  fourth 
metatarsal  bones.  Its  insertion  is  expanded  much  more 
than  the  peroneus  longus,  and  owing  to  the  firm,  spreading, 
tentacle-like  grip  it  has  of  the  sole  of  the  foot  the  insertion 
has  been  likened  to  a  hand. 

Peroneus  Longus. — The  muscle  lies  superficial  to  the 
peroneus  brevis,  and  arises  from  the  head  and  upper  two 
thirds  of  the  outer  surface  of  the  fibula.  Its  tendon  passes 
with  that  of  the  brevis  behind  the  outer  malleolus,  which 
forms  a  pulley  round  which  the  tendon  plays,  and  so  has 
its  function  increased.  Running  on  the  outer  side  of  the 
os  calcis  to  the  cuboid  it  enters  the  sole  of  the  foot,  across 
which  it  runs  obliquely  to  be  inserted  into  the  base  of  the 
metatarsal  bone  of  the  great  toe,  and  to  the  internal 
cuneiform  bone  as  well.  Both  behind  the  outer  malleolus 
and  on  the  outer  side  of  the  os  cuboid,  where  the  tendon 
alters  its  direction,  it  is  thickened.  Whilst  the  outer  mal- 
leolus acts  as  a  pulley  for  the  muscle,  it  is  interesting  to 
note  that  at  the  os  cuboid,  where  it  is  entering  the  sole 
of  the  foot,  a  fibro-cartilage  is  formed  in  the  tendon  which 
plays  by  means  of  a  bursa  over  a  smooth  tubercle  on  the 
cuboid  bone. 

MUSCULAR    ACTIONS 
I.     Flexion  and  Extension 

In  the  movements  of  pure  flexion  and  extension  of  the 
foot,  without  inversion  or  eversion,  bending  (dor  si-flex  ion) 
is  produced  by  the  tibialis  anticus,  peroneus  tertius,  and 
peroneus  brevis,  and  extending  (plantar-flexion)  by  the 
gastrocnemius,  soleus,  plantaris,  tibialis  posticus,  and 
peroneus  longus.     The  front  of  the  leg  and  dorsum  of  the 


174  THE    ACTION    OF    MUSCLES 

foot  belong  morphologically  to  the  general  extensor  surface 
of  the  limb,  corresponding  with  the  back  of  the  forearm 
and  the  dorsum  of  the  hand.  The  back  of  the  leg  and  sole 
of  the  foot  correspond  with  the  front  of  the  forearm  and 
palm  of  the  hand,  so  that  what  we  call  flexion  is  really 
over-extension.  It  is  usual,  however,  and  it  will  be  followed 
here,  to  use  the  term  flexion  for  the  movement  by  which  the 
dorsum  of  the  foot  is  bent  towards  the  front  of  the  leg  ; 
and  extension  to  the  movement  by  which  the  sole  of  the 
foot  is  directed  towards  the  back  of  the  leg.  In  the  move- 
ments of  flexion  and  extension  at  the  ankle  three  principles 
of  leverage  are  illustrated. 

(a)  If  we  raise  the  foot  from  the  ground  and  then  extend 
it  so  as  to  point  the  toes,  .we  illustrate  a  lever  of  the  first 
order,  the  fulcrum  or  ankle  joint  lying  between  the  power 
of  the  tendo  achillis  at  the  calcaneus  and  the  weight  or 
front  of  the  foot  which  offers  the  resistance  (fig.  2,  p.  10). 

(b)  When  we  stand  on  tip-toe  we  illustrate  the  second 
variety  of  lever — the  fulcrum  being  at  the  ball  of  the  toes  ; 
the  power  is  applied  by  the  muscles  of  the  calf  at  the  os  calcis, 
and  between  the  two  is  the  weight  to  be  raised,  which  is  that 
of  the  body  communicated  through  the  tibia  (fig.  3,  p.  n). 

(c)  If  we  raise  one  foot  from  the  ground  and  flex  it  we 
illustrate  a  lever  of  the  third  order,  the  power  represented 
by  the  insertion  of  the  tibialis  anticus,  peroneus  tertius, 
and  peroneus  brevis,  lying  between  the  weight,  or  front  of 
the  foot,  and  the  fulcrum  at  the  ankle-joint. 

The  chief  flexor  of  the  foot  on  the  leg  is  the  tibialis 
anticus  and  the  chief  extensors  are  the  gastrocnemius, 
soleus,  and  plantaris  acting  through  the  tendo  achillis. 
The  disparity  in  size  between  the  extenders  and  the  flexors 
is  very  evident,  and  while  the  tibialis  anticus  may  weigh 
only  5  oz.,  the  gastrocnemius  and  soleus  may  weigh  five 
times  that  amount. 

The  muscles  acting  through  the  tendo  achillis  on  each 
side,  when  they  take  their  fixed  point  above,  are  important 
muscles  in  running,  walking,  jumping,  and  standing  on  tip- 
toe, in  which  their  action  is  against  gravity  and  the  body 


MUSCLES  ACTING    ON    THE    FOOT 


175 


weight,  hence  their  size  and  strength.  When  we  stand, 
their  fixed  point  is  at  the  heel,  and  they  are  important 
factors  in  keeping  the  body  from  inclining  the  tibia  and 
fibula  forwards  at  their  articulation  with  the  astragalus. 
These  muscles  (fig.  63,  p.  128)  thus  steady  the  leg  on  the  foot 


EXTENDERS 
OF  ANKLE 


FLEXORS 
OF  ANKLE 


Fig.  84. — Extension  backwards  of  the  rigid  body  at  the  ankle  joint. 


and  help  to  prevent  the  body  from  falling  forwards.  The 
gastrocnemius  has  been  described  not  only  as  an  extensor 
of  the  foot,  but  as  a  flexor  of  the  knee  as  well.  It 
does  not  act  on  the  knee  joint.  Its  contraction  is  not 
necessarily  associated  with  relaxation  of  the  quadriceps. 
That   is   only   associated   with  muscles  having  the   same 


176  THE    ACTION    OF    MUSCLES 

centre  for  motion,  the  flexors  of  the  knee.  We  can  extend 
at  the  ankle  in  either  the  position  of  flexion  or  extension 
of  the  knee.  The  best  illustration  of  the  action  of  the 
flexors  and  extensors  of  the  ankle  when  they  take  their 
fixed  point  from  below,  viz.  the  foot,  is  seen  in  certain 
acrobats.  These,  when  standing  with  the  hip  and  knee 
joints  in  the  position  of  extension,  can  bend  the  body 
forward  in  one  piece  at  the  ankle,  so  as  to  pick  an  object 
off  the  ground  (flexors  of  the  ankle),  and  can  extend  the 
body  at  the  ankle  back  to  the  erect  position  (extensors  of 
the  ankle).  Thus  we  see  the  necessity  for  strong  extensors 
which  can  bring  the  body  back  against  gravity — the  soleus 
gripping  the  tibia  and  fibula,  and  the  gastrocnemius  the 
femur.  From  the  position  of  equilibrium  at  the  ankle  in 
the  erect  posture,  in  which  the  powerful  extensors  of  the 
ankle  antagonize  not  only  the  flexors,  but  also  gravity,  the 
calf  muscles  are  able  to  produce  a  limited  amount  of  exten- 
sion backwards  of  the  rigid  body  at  the  ankle  joint,  as  shown 
in  fig.  84.  This,  like  so  many  of  the  reverse  actions  of  the 
lower  extremity,  is  best  seen  in  athletes. 

In  talipes  calcaneus  (fig.  85B),  the  result  usually  of  polio- 
myelitis in  childhood,  the  functions  of  the  muscles  of  the 
calf  (extenders)  are  weakened  and  the  unrestrained  flexors 
contract,  producing  the  attitude  of  flexion  at  the  ankle 
joint.  In  this  condition  there  may  only  be  an  acute 
angle  between  the  dorsum  of  the  foot  and  front  of  the 
leg,  and  in  some  severe  cases  the  two  may  actually  be 
in  contact.  The  patient  walks  on  the  heel.  In  talipes 
equinus  (fig.  85A),  which  is  usually  also  the  result  of 
poliomyelitis,  the  opposite  condition  is  present.  The 
flexors  are  paralysed,  and  the  extensors  contract  and 
shorten,  resulting  in  the  tense  unyielding  tendo  achillis 
requiring  operative  lengthening  to  produce  muscular 
equilibrium,  and  so  to  overcome  the  deformity.  The  heel 
is  drawn  up,  and  in  severe  cases  may  actually  form  a 
straight  line  with  the  leg.  The  patient  walks  on  the  balls 
of  the  toes,  which,  in  walking,  form  a  right  angle  with 
the  foot. 


MUSCLES    ACTING    ON    THE    FOOT  177 

II.  Inversion  and  Eversion 
(a)  Inversion. — When  we  speak  of  the  tibialis  anticus, 
peroneus  tertius,  and  peroneus  brevis  as  being  flexors  of 
the  foot,  and  the  tibialis  posticus  and  peroneus  longus  as 
being  extensors,  we  mean  that  as  regards  eversion  and 
inversion  of  the  foot,  these  muscles  are  then  in  a  state 
of  equilibrium.  They  are  evenly  balanced  as  regards 
those  particular  functions,  so  that  we  thus  obtain  a  pure 
flexion  and  extension  at  the  ankle  without  any.  lateral 
deviations.  Why  we  have  two  inverters  (the  tibialis 
anticus  and  posticus),  and  two  principal  everters  (the 
peroneus  longus  and  brevis),  is  to  allow  of  either  inver- 
sion or  eversion  in  the  position  of  either  flexion  or  extension 
of  the  foot.  Turning  the  foot,  either  in  or  out,  can  take 
place  in  the  position  of  flexion  or  extension,  and  each 
movement  must  be  evenly  opposed.  Inversion  with  flexion 
is  produced  by  the  tibialis  anticus,  and  eversion  in  the 
flexed  position  by  the  peroneus  brevis,  assisted  by  the 
peroneus  tertius  when  present.  Inversion  with  extension 
is  produced  by  the  tibialis  posticus  (fig.  87,  p.  194),  and 
eversion  with  extension  is  produced  by  the  peroneus  longus. 
These  movements  would  appear  to  be  associated  with  the 
arboreal  habit  of  man's  ancestors  to  which  Professor  Wood 
Jones  has  directed  our  attention. 

If  when  sitting  we  raise  the  foot  off  the  ground  and 
extend  it  at  the  ankle,  the  tibialis  anticus  and  the  other 
flexors  relax  and  elongate,  and  the  extensors  contract 
and  shorten.  If  we  then  invert  the  foot  in  the  extended 
position,  this  is  due  to  further  contraction  of  the  tibialis 
posticus,  and  its  tendon  can  be  felt  to  rise  up  close 
to  its  insertion  at  the  navicular  or  scaphoid  bone.  It 
is  interesting  to  note  that  in  cases  of  acquired  talipes 
equinus  (fig.  85A),  with  the  patient  walking  on  the  balls  of 
the  toes,  it  is  rarely  necessary  to  do  more  than  elongate 
the  tendo  achillis.  Should  there  be  any  inversion  of  the 
foot  (varus)  it  is  the  tibialis  posticus  that  requires  division. 
If,  when  sitting,  we  raise  our  foot  off  the  ground  and  flex  it 
12 


17.8  THE.  ACTION    OF    MUSCLES 

at  the  ankle,  the  tibialis  anticus,  peroneus  tertius,  and 
peroneus  brevis  contract  and  shorten  ;  the  muscles  uniting 
at  the  tendo  achillis,  together  with  the  peroneus  longus  and 
tibialis  posticus,  relax  and  elongate.  If  we  now  invert  the 
foot  the  hollow  over  the  tibialis  anticus  on  the  front  of  the 
leg,  associated  with  its  contraction  for  flexion,  becomes  dis- 
tinctly deepened  and  the  tendon  stands  out  more  prominently 
on  the  inside  of  the  foot.  In  a  condition  of  equilibrium 
of  the  muscles  acting  on  the  foot,  in  which  the  latter  is 
midway  between  flexion  and  extension,  and  between  inver- 
sion and  eversion,  inversion  of  the  foot,  in  which  the  inner 
border  is  raised  and  the  sole  looks  inward,  would  be  the 
result  of  the  combined  action  of  the  two  tibial  muscles. 

In  an  arboreal  animal  like  the  marsupial  koala,  in 
which  the  big  toe  can  oppose  like  a  thumb  and  the 
fibula  approaches  the  tibia  in  size,  the  importance  of 
good  inversion  and  eversion  of  the  foot  is  obvious.  The 
evolutionary  evidence  derived  from  a  study  of  the  foot 
of  the  kangaroo  especially  seems  to  show  that  the  tibialis 
anticus  or  flexing  inverter  is  "  selected  "  in  preference  to 
the  tibialis  posticus  or  extending  inverter.  In  the  salta- 
torial  kangaroo,  which  may  reach  8  feet  in  height  and 
whose  leap  may  vary  from  25  to  30  feet,  eversion  of  the  foot 
— which  practically  consists  of  one  main  toe — is  prevented 
by  the  retention  of  a  very  powerful  muscular  tibialis  anticus. 
In  this  animal  I  have  often  found  the  posticus  to  be  absent, 
and  when  present  to  consist  of  nothing  more  than  a  tendinous 
shred  about  the  thickness  of  strong  cotton.  In  the  kangaroo 
the  fibula  can  be  regarded  as  non-existent  as  a  separate 
bone.  For  its  lower  two  thirds  it  has  become  attached  to 
the  tibia,  in  which  it  is  becoming  incorporated,  just  as  the 
appendix  is  in  the  wall  of  the  ileum  in  the  wombat,  and 
the  right  adrenal  is  in  the  liver  of  the  Australian  phalanger. 
In  cases  of  congenital  defects  of  the  fibula  in  the  human 
subject,  which  are  associated  with  eversion  of  the  foot,  the 
condition  in  the  kangaroo's  foot  points  the  way  towards  treat- 
ment (fig.  5,  p.  32).  A  bone  which  in  the  human  species  is 
obviously  undergoing  disappearance  is  scarcely  one  in  which 


MUSCLES    ACTING    ON    THE    FOOT  179 

to  expect  reparative  changes  from  bone  grafting.  The 
indication  is  to  develop  the  tibialis  anticus  as  powerfully  as 
possible.  This  can  be  done  by  resting  the  foot  at  night  in 
a  shoe  in  which  the  member  is  flexed  and  inverted,  and  by 
encouraging  the  patient  to  walk  on  the  outside  of  the  foot 
by  having  the  inside  of  the  boot  arched  at  the  instep,  and 
the  sole  and  heel  raised  on  the  inner  side.  This  method  I 
have  seen  successfully  carried  out  in  several  cases. 


Fig.  85. — Acquired  deformities  of  the  foot. 
A,  Equinus.     b,  Calcaneus,     c,  Varus.     r>,  Valgus. 


(b)  Eversion. — In  a  condition  of  equilibrium  of  the  loot 
as  regards  eversion  or  inversion,  the  peroneus  longus,  which  is 
inserted  on  the  sole  of  the  foot,  acts  as  an  accessory  extender, 
and  the  peroneus  brevis,  which  is  inserted  on  the  dorsum  of 
the  foot,  acts  as  an  accessory  bender.  The  peroneus  brevis 
does  not,  as  is  usually  taught,  help  to  extend  the  foot  on  the 
leg,  antagonizing  the  tibialis  anticus  and  peroneus  tertius, 


i8q  THE    ACTION    OF    MUSCLES 

which  flex.  On  the  contrary,  it  is  an  accessory  muscle  to 
these  latter.  If  we  raise  the  foot  off  the  ground  and  flex 
it,  this  latter  movement  is  performed  by  the  tibialis  anticus, 
peroneus  tertius,  and  peroneus  brevis  ;  the  tendo  achillis 
muscles  and  the  peroneus  longus  and  tibialis  posticus — 
being  relaxed  and  elongated.  If  now  we  evert  the  foot, 
this  eversion  is  produced  by  further  action  of  the  peroneus 
brevis,  assisted  by  the  tertius,  which  are  both  in  a  physio- 
logical state  of  contraction.  If  we  raise  the  foot  off  the 
ground  and  extend  it,  this  movement  is  performed  by  the 
muscles  of  the  tendo  achillis  and  the  tibialis  posticus  and 
peroneus  longus — the  tibialis  anticus,  peroneus  tertius,  and 
peroneus  brevis  being  in  a  physiological  state  of  relaxation. 
If  now  we  evert  the  foot,  this  action  is  produced  by  the 
peroneus  longus,  which  is  in  a  physiological  state  of  con- 
traction. Thus  the  two  peronei,  though  inserted  differently, 
produce  in  different  states  of  the  ankle  a  similar  result — the 
one  turning  the  outer  edge  of  the  foot  up  and  the  other 
turning  the  inner  edge  down.  If  the  foot  be  in  a  condition 
of  equilibrium  as  regards  flexion  and  extension,  eversion  of 
the  foot  is  produced  by  the  combined  action  of  the  peronei. 
When  they  take  their  fixed  point  from  below  the 
peronei  and  the  tibiales  help  to  maintain  the  erect  posture 
by  steadying  the  leg  on  the  foot,  which  is  especially 
evident  when  we  stand  on  one  leg — the  opposing  and 
balanced  groups  not  only  strengthening  the  ankle  joint, 
but  preventing  the  body  from  falling  to  one  side  or  the 
other.  The  peroneus  longus,  by  its  insertion  at  the  ball 
of  the  great  toe  enabling  the  inner  edge  of  the  foot  to  be 
turned  down  to  the  ground,  is  especially  serviceable  when 
we  stand  on  tip-toe,  whereby,  with  the  feet  separated  and 
everted  and  the  ankle  extended,  the  weight  of  the  body  is 
transmitted  to  the  ground  mainly  through  the  ball  of  the 
big  toe.  Hence  in  man  the  importance  of  this  muscle  in 
walking,  running,  and  jumping.  Its  action  is  especially 
well  exemplified  in  dancing  and  skating.  It  is  at  the  ball 
of  the  big  toe  that  severe  pain  is  often  felt  after  a  long 
walk. 


MUSCLES    ACTING    ON    THE    FOOT  181 

From  the  point  of  view  of  selection,  however,  it  would 
appear  that  the  action  of  the  peroneus  longus  is  of  less 
importance  than  that  of  the  peroneus  brevis.  The  brevis 
in  man  is  muscular,  practically  down  to  the  malleolus,  and 
just  above  the  malleolus  its  size  is  about  twice  that  of  the 
longus,  which  hugs  it  closely.  In  the  koala,  with  its  oppos- 
able big  toe,  the  longus  has  a  well-defined  use,  being  traced  to 
the  hallux  and  acting  as  an  adductor  ;  and  in  the  anthropoid 
it  is  a  grasping  muscle,  acting  as  a  flexor  of  the  metatarsal 
bone  of  the  hallux.  In  the  wombat,  with  a  diminutive 
big  toe,  we  have  a  relative  diminution  in  size  of  the  longus, 
which  is  plainer  seen  in  the  kangaroo.  Here  the  peroneus 
longus  is  practically  non-existent,  so  it  cannot  be  of  the 
importance  in  retaining  the  foot  on  the  ground  previously 
imagined.  In  this  animal  the  longus  attachment  is  retreat- 
ing laterally,  and  a  retreating  muscle  is  a  weakening  one  ; 
and  this  is  further  contrasted  by  the  greater  belly  muscu- 
larity of  the  brevis.  In  the  koala  I  have  noted  laterally 
on  the  dorsum  of  the  foot  two  peronei  accessory  to  the 
peroneus  brevis.  In  a  case  of  valgus  (eversion)  (fig.  85D), 
in  which  the  patient  walks  on  the  inside  of  the  foot,  the  con- 
dition at  the  ankle  being  neither  that  of  extension  (equino- 
valgus)  nor  flexion  (calcaneo-valgus) ,  should  we  desire  to 
weaken  eversion  without  abolishing  it,  the  principle  on  com- 
parative lines  would  be  to  divide  the  stronger  and  selected 
everter  (peroneus  brevis),  and  to  retain  the  weaker  everter 
(peroneus  longus) . 


CHAPTER  X 

THE  MUSCLES  OF  THE  TOES  (GREAT  SCIATIC 

NERVE) 

These  may  be  considered  under  two  divisions  : 

(i)  Those  which  move  the  hallux  or  big  toe. 
(2)  Those  which  move  the  four  lesser  toes. 

I.     MUSCLES    ACTING    ON    THE    HALLUX 

These  are  : 

(a)  Two  extensors. — Extensor  longus  hallucis  and  ex- 

tensor brevis  digitorum  (innermost  tendon). 

(b)  Two  flexors. — Flexor   longus   hallucis    and   flexor 

brevis  hallucis. 

(c)  Abductor  hallucis. 

(d)  Adductor  hallucis. 

Extensor  Longus  Hallucis. — This  slender  muscle  arises 
from  the  middle  two  fourths  of  the  front  of  the  fibula  and 
the  adjacent  interosseous  membrane,  and  its  tendon,  after 
crossing  the  front  of  the  ankle,  is  inserted  into  the  base  of 
the  distal  phalanx  of  the  great  toe. 

Extensor  Brevis  Digitorum. — This  arises  on  the  dorsum 
of  the  foot  from  the  front  part  of  the  superior  surface  of 
the  os  calcis,  and  from  the  outer  or  lateral  extremity  of  the 
anterior  annular  ligament.  Passing  forward  on  the  dorsum 
of  the  foot  it  gives  rise  to  four  muscular  bellies,  the  two 
inner  of  which  are  the  larger.  These  bellies  terminate  in 
four  tendons.  The  innermost  tendon  (extensor  brevis 
hallucis)  is  inserted  into  the  dorsal  surface  of  the  base  of 

182 


THE    MUSCLES    OF   THE   TOES 


183 


the  proximal  phalanx  of  the  great  toe.  The  remaining 
tendons  pass  to  the  adjacent  three  lesser  toes.  In  mono- 
tremata  (platypus  and  echidna)  this  muscle  mainly  arises 
from  the  fibula  ;  but  with  higher  mammalian  development 
it  gradually  recedes  from  the  leg  to  the  foot,  and  the  peroneus 
tertius  represents,  as  stated,  the  remains  of  its  fibula  origin. 
The  long  extender  (extensor  longus  hallucis)  has  its 
fulcrum  at  the  interphalangeal  joint  of  the  big  toe.  It 
extends  the  distal  phalanx  of  the  hallux.  It  does  not 
flex  at  the  ankle  joint,  as  is  commonly  taught.     By  its 


FLEXOR  BREVIS 


ADDUCTOR 
FLEXOR LONGUS 


PERONEUS  LONQUS 


EXT:  LONGUS 


EXT.  BREV/S 
ABDUCTOR 


Fig.  86. — The  muscles  of  the  big  toe  (hallux). 

action  the  extensors  of  the  ankle  are  not  called  into  a 
state  of  relaxation.  This  can  only  happen  when  the 
flexors  of  the  ankle  (tibialis  anticus,  peroneus  brevis, 
and  peroneus  tertius)  contract.  The  short  extensor  has 
its  fulcrum  at  the  metatarso-phalangeal  joint.  It  pro- 
duces extension  there,  acting  on  the  proximal  phalanx. 
It  is  interesting,  then,  to  note  that  the  big  toe  has  two 
separate  extending  muscles.  In  children  with  talipes 
varus  (inversion  of  the  foot)  division  of  the  tibialis  anticus 
is  usually  required.  Its  proximity  to  the  extensor  longus 
hallucis  should  be  remembered,  as  the  two  are  sometimes 
divided  in  a  subcutaneous  tenotomy,  with  subsequent 
"  dropped    toe "    deformity.     The    operation    in    children 


1 84  THE    ACTION    OF    MUSCLES 

should  always  be  an  open  one,  and  the  extensor  hallucis 
should  be  identified  and  hooked  out  of  the  way. 

It  is  worth  remembering  that  the  extensor  longus  hallucis 
and  extensor  longus  digit orum  are  held  down  by  the  annular 
ligaments  or  straps,  so  as  to  follow  the  contour  of  the  ankle 
and  dorsum  of  the  foot.  They  do  not  take  the  shortest 
course  to  the  toes.  If  they  did,  just  as  in  the  case  of  the 
biceps  brachii  without  the  bicipital  fascia,  this  would 
result  in  prominence  and  so  in  liability  to  injury.  Although 
the  short  course  would  have  resulted  in  improvement  of 
strength  of  action,  velocity  of  action  would  be  diminished, 
and  the  toes  rendered  less  elastic  and  more  rigid.  If 
tendons  were  not  firmly  held  in  relation  to  bones,  but  were 
allowed  to  rise  during  muscular  action,  the  effects  of  such 
action  would  be  to  a  large  extent  negatived. 

Flexor  Longus  Hallucis. — This  muscle  arises  at  the  back 
of  the  leg  from  the  lower  two  thirds  of  the  posterior  or 
dorsal  surface  of  the  fibula.  Its  tendon  passes  in  grooves 
on  the  back  of  the  lower  end  of  the  tibia — on  the  back  of 
the  astragalus — and  on  the  under  surface  of  the  sustenaculum 
of  the  calcaneus.  It  then  enters  the  sole  of  the  foot,  where 
it  is  displayed  in  the  dissection  of  the  second  layer  of 
muscles,  and  is  finally  inserted  into  the  base  of  the  distal 
phalanx  of  the  great  toe. 

Flexor  Brevis  Hallucis. — This  muscle  is  placed  on  the 
inner  side  of  the  sole  of  the  foot,  corresponding  to  the  meta- 
tarsal bone  of  the  hallux,  and  is  demonstrated  in  the  dissec- 
tion of  the  third  layer  of  muscles  on  the  sole.  It  arises  by 
a  pointed  tendon  from  the  inner  side  of  the  cuboid  bone 
and  the  tendinous  insertion  of  the  tibialis  posticus.  Passing 
forward,  its  muscular  belly  separates  into  two  portions,  each 
of  which  terminates  in  a  tendon  which  is  inserted  on  either 
side  of  the  base  of  the  proximal  phalanx  of  the  big  toe.  On 
each  tendon  a  sesamoid  bone  is  developed.  The  inner 
tendon  blends  with  the  abductor  hallucis  and  the  outer  with 
the  adductor  hallucis.  The  long  flexor  is  the  bender  at  the 
interphalangeal  joint  of  the  big  toe,  acting  on  the  distal 
phalanx.     It  is  the  antagonist  of  the  long  extensor.     The 


THE    MUSCLES    OF    THE    TOES  185 

short  flexor  produces  bending  at  the  metacarpo-phalangeal 
joint,  acting  on  the  proximal  phalanx.  It  is  the  antagonist 
of  the  short  extensor. 

One  cannot  fail  to  admire  the  means  adopted  by  nature 
to  effect  leverage  so  as  to  improve  the  action  of  the  flexors 
of  the  big  toe.  In  each  tendon  of  the  flexor  brevis  hal- 
lucis  a  sesamoid  bone  is  developed,  by  means  of  which, 
as  in  the  case  of  the  quadriceps  and  the  patella,  the  power 
of  the  muscle  is  improved.  But,  in  addition,  as  the 
muscular  belly  of  the  flexor  brevis  separates  into  two 
portions,  a  canal  is  formed  by  the  two  heads  along  which 
the  flexor  longus  passes  to  the  distal  phalanx,  and  the 
tendons  of  each  belly,  supported  by  the  sesamoids,  thus 
form  a  pulley  for  the  free  action  of  the  long  flexor.  The 
great  use  of  the  flexor  longus  hallucis  is  to  keep  the  big  toe 
in  contact  with  the  ground  when  we  walk,  being  an  important 
factor  in  raising  the  body  on  the  great  toe.  This  is  especi- 
ally seen  after  accidents  dividing  the  tendon,  when,  with  the 
big  toe  extended  from  over-action  of  the  long  extensor,  we 
lose  that  "  springiness  "  on  the  foot  so  important  in  the 
propulsion  of  the  body. 

Abductor  Hallucis. — This  is  found  amongst  the  first  layer 
of  muscles  on  the  sole.  Its  bony  origin  is  from  the  inner 
knob  on  the  under  surface  of  the  calcaneus.  Its  muscular 
belly  terminates  in  the  tendon  which  is  inserted  into  the 
inner  or  medial  side  of  the  base  of  the  proximal  phalanx 
of  the  big  toe. 

Adductor  Hallucis. — This  consists  of  two  portions,  an 
oblique  and  a  transverse  portion.  These  are  demonstrated 
in  a  dissection  of  the  third  layer  of  muscles  on  the  sole. 
The  oblique  portion  arises  from  the  sheath  of  the  peroneus 
longus  tendon  and  the  bases  or  tarsal  extremities  of  the 
third  and  fourth  metatarsal  bones.  The  transverse  portion 
is  narrow,  and  is  placed  transversely  across  the  distal  or 
phalangeal  extremities  of  the  metatarsal  bones.  This 
portion  arises  from  the  plantar  ligaments  of  the  three  outer 
toes.  The  two  portions,  together  with  the  outer  tendon  of 
the  flexor  brevis  hallucis,  blend  at  their  termination  and  are 


i86  THE    ACTION    OF    MUSCLES 

inserted  into  the  outer  side  of  the  base  of  the  proximal 
phalanx  of  the  big  toe.  The  transverse  portion  of  the 
adductor  hallucis  was  wrongly  described  by  the  older 
anatomists  under  the  name  of  transversus  pedis.  It  was 
regarded  as  arising  from  the  big  toe,  and  as  being  inserted 
into  the  fore  part  of  the  metatarsus  of  the  little  toe  so  as  to 
act  as  an  adductor  minimi  digiti.  As  the  little  toe,  which 
is  struggling  hard  to  retain  its  place  in  the  human  foot,  has 
an  adducting  interosseous,  it  is  difficult  to  understand  why 
the  adducting  power  of  the  little  toe  should  be  strengthened 
in  preference  to  that  of  the  "  selected  "  toe  or  hallucis. 
A  study  of  the  adductor  transversus  in  the  gorilla  shows 
that  this  is  one  of  the  short  muscles  giving  grasping  power 
to  the  hind  thumb  or  hallux. 

The  adductor  hallucis  draws  the  big  toe  outwards  towards 
the  lesser  toes.  The  abductor  hallucis  draws  the  big  toe 
inwards  away  from  the  lesser  toes.  The  plane  for  abduction 
and  adduction  corresponds  to  the  axis  of  the  second  toe. 
The  transverse  part  of  the  adductor,  by  its  contraction,  draws 
not  only  the  big  toe  towards  the  lesser  toes,  but  approxi- 
mates also  the  heads  of  the  metatarsal  bones  so  as  to 
increase  the  curve  of  the  transverse  arch  of  the  metatarsus. 
This  denotes  that  origin  and  insertion  of  muscle  approxi- 
mate. There  is  no  necessity,  however,  for  hollowing  or 
M  guttering  "  of  the  foot,  and  this  transverse  portion  should 
be  looked  on,  like  the  oblique  portion,  as  a  pure  adductor 
of  the  hallux.  Apart  from  this  action  the  front  of  the  foot 
is  strengthened  by  the  support  given  by  a  transverse  band 
of  muscle,  with  the  power  of  contraction  and  relaxation  in 
preference  to  the  less  perfect  support  of  a  transverse  liga- 
ment. 

As  there  is  not  the  freedom  of  lateral  movement  in  the 
great  or  lesser  toes  to  the  same  extent  as  in  the  fingers, 
we  are  apt  to  think  that  abduction  and  adduction  are  of 
little  importance.  Interference  with  the  lateral  movement 
of  the  big  toe,  however,  is  the  cause  of  what  is  perhaps  the 
most  common  factor  interfering  with  gait  in  modern  life, 
namely  bunion  of  the  big  toe,  which  is  associated  with  the 


THE    MUSCLES    OF    THE    TOES  187 

pathological  condition  known  as  hallux  valgus.  This  I 
have  invariably  found  associated  with  flat  foot.  In  hallux 
valgus  the  head  of  the  metatarsal  bone  of  the  big  toe 
projects  on  the  inside  of  the  foot,  and  the  phalangeal  seg- 
ment is  directed  outwards  towards  the  other  toes.  An 
angular  deformity  results,  and  over  the  projection  a 
bursa  develops,  which  usually  becomes  thickened  and 
inflamed.  This  condition  is  more  common  in  women  than 
in  men,  and  no  doubt  is  largely  dependent  on  the  narrow 
boots  usually  worn  interfering  with  the  spread  of  the  foot. 
The  condition  is  aggravated  by  high  heels  throwing  the 
body  weight  on  the  ball  of  the  great  toe. 

In  treatment  it  is  the  muscular  factor  we  have  to  con- 
sider, just  as  in  flat  foot.  No  one  presumably  regards 
yielding  of  plantar  ligaments  as  the  cause  of  flat  foot. 
The  essential  factor  in  flat  foot  is  muscular — strong 
everters  and  weakened  inverters.  Similarly,  in  hallux 
valgus  the  abductor  hallucis  as  the  result  of  pressure  is  in 
a  weakened  state,  analogous  to  a  paralysed  muscle — its 
action  for  years  having  been  interfered  with — and  the 
result  is  over- action  of  the  adductor  hallucis.  No  doubt  this 
weakness  of  the  abductor  hallucis  is  a  secondary  con- 
tributing factor  towards  the  condition  of  flat  foot.  In 
treatment  the  foot  should  be  kept  constantly  at  a  right 
angle  in  a  splint,  and  the  big  toe  held  forcibly  abducted, 
so  as  to  stretch  the  contracted  adductor  hallucis,  and  take 
the  strain  off  the  abductor  to  allow  it  possibly  to  recover. 
No  effect  can  be  obtained  in  less  than  eight  weeks,  and  the 
splint  should  be  worn  every  night  for  a  considerable  period 
afterwards,  daily  attempts  at  re-education  of  the  abductor 
being  made.  When  walking  is  permitted  the  boot  should 
be  arched  on  the  inside,  and  the  sole  and  heel  raised  along 
the  inner  edge,  so  as  to  take  all  strain  off  the  ball  of  the  toe. 

The  boot  should  be  broad  anteriorly  to  allow  of  spread 
for  the  toes,  and  is  best  at  first  laced  to  toe,  so  that  when 
the  boot  is  put  on  the  big  toe  can  be  abducted  by  wool 
before  lacing.  In  old  severe  cases  operation,  such  as 
excision  of  the  metatarso-phalangeal  joint,  may  be  neces- 


188  THE    ACTION    OF    MUSCLES 

sary.  Since  the  hallux  is  the  selected  toe  care  should  be 
taken  by  the  surgeon  to  avoid  if  possible  its  removal  in 
cases  of  accident.  Should  this  be  necessary,  the  power  not 
only  of  the  foot  but  of  the  leg  for  walking  and  standing  is 
greatly  impaired. 

II.     MUSCLES  ACTING  ON  THE  FOUR  LESSER  TOES 

These  are  : 

(i)  Extensors. — Extensor  longus  digitorum  and  exten- 
sor brevis  digitorum. 

(2)  Flexors. — Flexor   longus   digitorum,    flexor   acces- 

sorius,    flexor   brevis    digitorum,    flexor    brevis 
minimi  digiti,   and  lumbricales. 

(3)  Abductors  and  adductors. — Abductor  minimi  digiti 

and  dorsal  and  plantar  interossei. 

(1)  Extensors 

Extensor  Longus  Digitorum  arises  from  the  upper  three 
fourths  of  the  anterior  surface  of  the  fibula  and  from  the 
outer  tuberosity  of  the  tibia.  Its  tendon  passes  in  front  of 
the  ankle  and  divides  into  four  separate  slips  which  pass  to 
the  four  lesser  toes.  On  the  dorsum  of  the  foot  these 
tendons  pass  obliquely  from  within  outwards. 

Extensor  Brevis  Digitorum. — This  arises  on  the  dorsum 
of  the  foot,  from  the  front  part  of  the  superior  surface  of 
the  calcaneus  and  from  the  outer  extremity  of  the  anterior 
annular  ligament.  Passing  forward  on  the  dorsum  of  the 
foot  it  gives  rise  to  four  muscular  bellies,  the  two  inner  of 
which  are  the  larger.  These  bellies,  which  pass  obliquely 
from  without  inwards,  terminate  in  four  tendons.  The 
innermost  passes  as  described  to  the  great  toe,  and  the 
remaining  three  pass  to  the  second,  third,  and  fourth  toes, 
lying  on  the  outer  side  of  the  long  tendons. 

The  tendons  of  the  long  and  short  extensors  are  distinct 
on  the  dorsum  of  the  proximal  phalanges  of  the  second, 
third,  and  fourth  toes,  becoming  associated  at  the  distal 
extremity.  They  are  firmly  connected  to  the  proximal 
phalanx.     The  combined  tendon  is  traced  over  the  middle 


THE    MUSCLES    OF   THE   TOES  189 

to  the  distal  phalanx,  being  connected  with  both.  In  the 
case  of  the  little  toe,  which  appears  to  be  struggling  hard 
to  retain  its  place  in  the  foot,  the  short  tendon  is  absent, 
and  extension  is  produced  by  the  long  extender  only.  These 
muscles  extend  the  phalanges  of  the  second,  third,  fourth, 
and  fifth  toes,  and  it  would  seem  from  special  dissections  I 
have  made  in  reference  to  this  question,  that  motor  power 
for  extension  of  the  middle  and  distal  phalanges  is  largely 
derived  from  the  short  extender.  The  oblique  direction  of 
the  short  extending  tendons  counteracts  the  opposite 
obliquity  of  the  long  extenders,  so  that  when  the  two  act 
together — and  their  action  is  inseparable — we  have  an  even 
extension  of  the  toes.  Man  not  being  provided  like  the 
ape  with  an  opposable  hallux,  there  is  not  the  same  freedom 
of  the  toes  as  of  the  fingers,  nor  the  same  fine  co-ordinations. 

(2)  Flexors 

Flexor  Longus  Digitorum  (Perforans). — This  arises 
from  the  middle  three  fifths  of  the  dorsum  of  the  tibia,  and 
its  tendon  passes  behind  the  inner  malleolus  and  enters  the 
sole  of  the  foot,  where  it  is  demonstrated  in  a  dissection 
of  the  second  layer  of  muscles.  In  the  sole  it  is  joined  by 
the  flexor  accessorius,  and,  dividing  into  four  tendons  for 
the  second,  third,  fourth,  and  fifth  toes,  each  is  inserted 
into  the  base  of  the  distal  phalanx. 

Flexor  Accessorius. — This  small  fleshy  muscle  lies  on  the 
sole  of  the  foot,  and  arises  from  the  lower  part  of  the  cal- 
caneus by  two  divisions,  which  unite  and  are  inserted  into 
the  tendon  of  the  flexor  longus  digitorum  before  its  division. 
The  pull  of  the  flexor  longus  is  obliquely  from  within  out- 
wards. By  means  of  this  accessory  muscle,  not  only  is  the 
action  of  the  flexor  longus  strengthened,  but  its  pull  on  the 
toes  is  made  in  a  directly  backward  direction  instead  of 
inwards.  It  is  interesting  to  note  that  Cowper  considered 
the  accessorius  as  part  of  the  lumbricales.  It  was  his 
opinion  that,  just  as  the  long  flexor  divided  into  four  tendons, 
so  also  did  the  accessorius  divide  into  the  fleshy  muscles  or 
lumbricales. 


190  THE    ACTION    OF    MUSCLES 

Flexor  Brevis  Digitorum  (Perf  oratus).— This  forms  the 
middle  of  the  first  layer  of  the  muscles  on  the  sole  of  the 
foot.  It  arises  from  the  plantar  fascia  and  the  inner  or 
medial  tubercle  of  the  calcaneus,  and  its  muscular  belly 
divides  into  four  tendons  for  the  four  lesser  toes.  Each 
tendon  at  the  base  of  the  proximal  phalanx  divides  into  two 
to  allow  of  the  passage  of  the  long  tendon — these  two 
portions  then  unite  to  form  a  grooved  channel  for  the  long 
tendon — and  they  finally  separate  and  are  inserted  on  each 
side  of  the  middle  phalanx.  This  arrangement  of  the  long 
and  short  flexors  is  analogous  to  that  of  the  profundus  and 
sublimis  on  the  fingers,  and  by  this  arrangement  space  is 
economized  and  a  double  system  of  leverage  improvised, 
as  explained  in  the  description  of  the  finger  tendons. 

Flexor  Brevis  Minimi  Digiti. — This  arises  at  the  base  of 
the  metatarsal  bone  of  the  little  toe  and  the  sheath  of  the 
peroneus  longus  as  it  crosses  the  sole  of  the  foot,  and  is 
inserted  into  the  base  of  the  proximal  phalanx  of  the  little 
toe  internal  to  the  abductor.  This  muscle  assists  in  bending 
the  little  toe  at  the  metacarpo-phalangeal  articulation. 

Lumbricales. — These  are  four  in  number,  and  arise  in  the 
sole  of  the  foot  from  the  tendons  of  the  flexor  longus  digi- 
torum. Each  lumbrical  ends  in  a  tendon  which  is  traced 
forward  on  the  inner  side  of  the  four  lesser  toes  to  the 
inner  dorsal  portion  of  the  base  of  each  proximal  phalanx. 
There  is  a  fibrous  connection  on  the  dorsum  of  the  proximal 
phalanges  between  the  interossei,  lumbricales,  and  extensor 
tendons.  As  regards  the  action  of  the  flexors  of  the  toes, 
the  lumbricales  by  acting  on  the  proximal  phalanges,  bend 
at  the  metatarso-phalangeal  joints  of  the  four  lesser  toes. 
The  flexor  brevis  bends  at  the  first  interphalangeal  joint 
owing  to  its  attachment  to  each  middle  phalanx,  and  the 
flexor  longus  bends  at  the  second  interphalangeal  joint 
owing  to  its  attachment  to  the  distal  phalanx.  The  flexor 
longus,  although  it  arises  in  the  leg,  does  not  extend  at  the 
ankle  joint  so  as  to  assist  the  gastrocnemius  and  soleus  in 
walking.  It  can  act  in  either  the  position  of  flexion  or 
extension  of  that  joint.     By  curving  into  the  sole  of  the 


THE    MUSCLES    OF   THE   TOES  191 

foot  round  the  inner  malleolus  improved  leverage  is  effected, 
—the  malleolus  acting  as  a  pulley  for  the  play  of  the  tendon. 
Although  the  obliquity  of  the  pull  of  the  long  flexor  is 
counteracted  mainly  by  the  accessorius,  the  short  flexor  is 
also  a  counteracting  force  against  the  oblique  pull,  since  it 
arises  from  the  calcaneus  and  its  tendons  rather  incline 
obliquely  inwards.  These  muscles  assist  walking  by  keep- 
ing the  toes  in  relation  to  the  ground. 


(3)  Abductors  and  Adductors 

Abductor  Minimi  Digiti  — This  is  seen  in  the  first  layer 
of  muscles  on  the  sole  of  the  foot  on  the  outer  or  lateral 
side.  It  arises  from  the  under  surface  of  the  calcaneus,  and 
is  inserted  into  the  outer  side  of  the  base  of  the  proximal 
phalanx  of  the  little  toe  external  to  the  flexor  brevis  minimi 
digiti.  Its  action  is  to  draw  the  little  toe  outwards  from 
the  others,  resembling  the  function  of  a  dorsal  interosseus. 

Interossei.  {a)  Dorsal. — These  are  four  in  number  and 
arise  by  two  heads  from  the  adjacent  sides  of  the  metatarsal 
bones.  Each  muscle  terminates  in  a  tendon  which  is 
traced  to  the  outer  side  of  the  bases  of  the  proximal  phalanx. 
The  first  two  pass  to  either  side  of  the  second  toe,  and  the 
remaining  two  to  the  outer  or  lateral  side  of  the  third  and 
fourth  toes.  The  big  and  little  toes  have  their  own  special 
abductors. 

(b)  Plantar. — These  are  three  in  number  and,  arising 
from  the  corresponding  metatarsal  bones,  pass  to  the  inner 
side  of  the  bases  of  the  proximal  phalanges  of  the  third, 
fourth,  and  fifth  toes.  The  big  toe  has  its  special  adductor, 
and  the  second  toe  has  a  dorsal  interosseus  on  either  side. 

In  the  foot  the  imaginary  line  for  the  lateral  action  of 
the  toes  passes  through  the  axis  of  the  second  toe.  In  the 
hand  the  line  of  action  is  to  or  from  an  imaginary  line 
through  the  axis  of  the  middle  finger.  Owing  to  the  diffe 
ences  in  the  adjustments  and  utility  of  the  hand  and  the 
foot  the  interossei  in  the  foot  of  man  have  not  the  importance 
they  have  in  the  hand.     The  dorsal  interossei  inserted  into 


192  THE    ACTION    OF    MUSCLES 

the  outer  sides  draw  the  toes  from  the  imaginary  line 
through  the  second  toe.  The  two  dorsal  interossei  for  the 
second  toe  oppose  each  other  and  abduct  separately  to  one 
or  other  side.  When  not  separately  in  action  they  main- 
tain an  equilibrium  as  regards  lateral  motion  in  this  toe, 
and  this  applies  equally  to  the  opposing  adductors  and 
abductors  in  the  other  four  toes.  The  plantar,  inserted  on 
the  inner  side,  adduct  or  draw  the  third,  fourth,  and  fifth 
toes  towards  the  second.  The  little  toe  is  abducted  by  the 
abductor  minimi  digiti,  and  the  big  toe  is  abducted  from 
the  second  toe  by  the  abductor  hallucis  and  drawn  to  it  by 
the  adductor  hallucis. 

Rest  and  Re-education  for  Muscles  acting  on  the 
Foot  and  Toes  (Sciatic  Nerve  Paralysis) 

There  is  not  the  same  specialization  of  function  in  the 
human  foot  as  compared  with  the  hand.  The  opposability 
of  the  hallux  to  the  toes  has  been  lost,  and  instead  of  a 
mechanism  like  the  hand,  which  might  almost  be  described 
as  "  cerebral,"  the  foot  has  become  merely  a  mechanical 
support  for  the  body.  A  person  who  has  lost  the  foot  may 
with  artificial  support  walk  so  well  that  the  defect  is  un- 
detected. In  the  upper  limb,  not  merely  the  loss  of  the 
hand,  but  even  of  one  muscle,  such  as  the  pronator  teres  or 
the  opponens  pollicis,  may  be  sufficient  to  ruin  the  utility 
of  the  limb.  Furthermore,  we  find  that  owing  to  the 
differences  in  the  control  of  the  nerves  of  the  hand  as  com- 
pared with  the  foot,  we  do  not  obtain  the  same  response  to 
rest  and  re-education  in  the  latter  as  in  the  former.  In 
treatment  an  essential  point  is  to  maintain  the  foot  at  a 
right  angle  with  the  leg.  By  this  I  do  not  mean  a  forced 
dorsi-flexion,  which  is  less  than  a  right  angle  and  an  uneasy 
position. 

The  foot  of  a  patient  which  is  in  the  position  of  "  cal- 
caneus "  (acute  flexion  at  the  ankle)  or  "  equinus  "  (acute 
extension  at  the  ankle)  is  in  a  position  of  comparative 
inutility.     By  maintaining  a  position  of  equilibrium  at  the 


THE   MUSCLES    OF   THE   TOES  193 

ankle  as  regards  flexion  and  extension  we  prevent  over- 
action  of  either  the  inverters  or  everters,  thus  preventing 
the  development  of  varus  (inversion)  or  valgus  (ever- 
sion).  The  most  common  cause  of  "  paralysis  "  in  the  leg 
and  foot  muscles  is  infantile  paralysis.  Trauma,  gunshot 
wound  or  other  injury  of  the  great  sciatic  or  peroneal 
(external  popliteal)  nerves,  are  also  not  uncommon  causes. 
What  we  are  apt  to  forget  is  that  the  injury  of  the  great 
sciatic  nerve  in  the  thigh  means  an  impairment  of  function 
on  both  the  dorsal  and  plantar  surfaces  of  the  foot.  Rarely 
in  cases  of  gunshot  wounds  of  the  back  of  the  thigh  do  we 
meet  with  interference  with  the  action  of  the  hamstrings. 
The  sartorius  and  gracilis  are  not,  we  must  remember, 
supplied  by  the  great  sciatic,  though  they  act  as  benders 
at  the  knee. 

Should  the  peroneal  (external  popliteal)  nerve  alone  be 
involved  there  is  interference  with  function  of  the  muscles 
of  the  front  and  outer  aspect  of  the  leg.  The  following 
movements  are  lost :  extension  of  the  toes  (long  and  short 
extenders)  ;  flexion  of  the  ankle  (tibialis  anticus,  peroneus 
longus,  and  peroneus  brevis)  ;  inversion  of  the  foot  in  the 
flexed  position  (tibialis  anticus)  ;  eversion  of  the  foot  in 
either  the  position  of  flexion  or  extension  (peroneus  brevis 
and  peroneus  longus).  In  a  case  of  recent  shell  wound  of 
the  outer  part  of  the  upper  leg,  which  had  involved  the 
peroneal  nerve  at  its  division  into  the  anterior  tibial  and 
musculo-cutaneous  branches,  the  patient  when  seen  had 
foot-drop,  with  a  contraction  of  the  tendo  achillis  and  slight 
tendency  to  inversion  (equino-varus) .  He  was  unable  to 
evert  in  either  the  position  of  flexion  or  extension  at  the 
ankle,  owing  to  weakness  of  both  the  peroneus  brevis  and 
peroneus  longus.  He  was  unable  to  invert  in  the  flexed 
position  at  the  ankle  owing  to  a  paralysed  tibialis  anticus  ; 
but  inverted  freely  in  the  extended  position  owing  to  free 
action  of  the  tibialis  posticus  supplied  by  the  posterior 
tibial  nerve  (fig.  87).  Such  a  foot  should  be  immediately 
rested  in  a  splint  with  the  foot-piece  at  a  right  angle,  and 
the  back-piece  should  extend  to  the  middle  of  the  thigh 
13 


i94 


THE    ACTION    OF    MUSCLES 


(fig.  93),  so  as  to  stretch  not  only  the  tendo  achillis  at  the 
ankle,  but  the  gastrocnemius  and  plantaris  at  the  knee. 
The  foot  should  be  placed  midway  between  inversion  and 
eversion,  and  the  toes  kept  hyper-extended  by  means  of 
wool.     Should,   in  such   cases,    contraction   of   the  tendo 


Fig.  87. — Inversion  of  the  foot  in  the  extended  position 
(tibialis  posticus). 

achillis  and  tibialis  posticus  be  severe,  lengthening  of  the 
tendons  may  be  necessary  in  order  to  remove  any  mechanical 
interference  with  recovery. 

The  patient  should  be  encouraged  to  make  frequent 
voluntary  attempts  at  extending  the  toes  and  flexing  the 
ankle  while  in  the  splint.     The  foot  should  also  be  lifted 


THE   MUSCLES    OF   THE   TOES  195 

out  of  the  splint  in  the  position  it  occupied  when  at  rest, 
the  heel  being  rested  on  the  palm  of  the  attendant's  left 
hand  and  slight  flexion  of  the  toes  and  extension  at  the 
ankle  allowed.  The  patient  is  then  encouraged  by  voluntary 
effort  to  regain  the  position  of  rest — the  amount  of  work 
being  gradually  increased.  Testing  for  minimum  function 
and  commencement  of  re-education  should  be  carried  out 
with  the  patient  lying  well  on  the  opposite  side,  the  lower 
limb  being  rotated  so  that  the  dorsal  surface  of  the 
affected  foot  looks  downward  and  the  plantar  surface 
upward.  This  position  can  be  initially  obtained  with  the 
patient  lying  on  his  face,  and  the  feet  hanging  over  the 
end  of  the  bed1 — the  ankles  being  meanwhile  supported 
on  a  pillow.  With  the  ankle  extended  (plantar  flexion)  we 
obtain  an  improved  leverage  for  the  weakened  muscles, 
in  addition  to  the  benefit  of  gravitational  effect.  The 
patient  is  gradually,  with  recovery,  brought  to  the  dorsal 
position. 

Should  the  internal  popliteal  nerve  be  involved  alone,  we 
find  the  foot  in  the  position  of  dorsi-flexion  at  the  ankle, 
owing  to  paralysis  of  the  muscles  acting  through  the  tendo 
achillis  and  of  the  tibialis  posticus.  There  is  also  inability 
to  invert  the  foot  in  the  extended  position  (tibialis  posticus) . 
Flexion  and  lateral  movements  of  the  toes  are  also  lost. 
In  this  condition  the  foot  should  be  rested  on  a  back  splint 
and  foot-piece.  The  foot-piece  should  be  extended  so  as 
to  allow  the  foot  to  be  in  the  position  of  equinus,  and  its 
extremity  bent  to  allow  flexion  of  the  toes.  The  back- 
piece  should  extend  to  the  middle  of  the  thigh  and  be  bent 
behind  the  knee  to  prevent  straining  of  the  gastrocnemius. 
Re-education  should  be  on  lines  opposite  to  that  for  the 
peroneal  nerve,  work  being  commenced  with  the  patient 
on  the  back  and  the  heel  dependent.  In  a  lesion  of  the 
great  sciatic  nerve  involving  all  the  muscles  of  the  front 
and  back  of  the  leg  and  foot,  the  foot  is  best  rested  in  the 
position  given  above  for  lesion  of  the  peroneal  (external 
popliteal)  nerve. 

As  regards  prognosis  and  treatment  in  this  condition  I 


1 96  THE    ACTION    OF    MUSCLES 

may  mention  the  case  of  a  boy  who  was  aged  nj  years 
when  seen,  and  was  suffering  from  "  paralysis "  of  the 
right  foot.  The  cause  was  infantile  paralysis.  The  leg 
and  foot  were  thin  and  cold,  and  the  boy,  when  walking, 
swung  the  foot  so  as  to  avoid  the  toes  dragging  on  the 
ground.  No  movements  of  the  toes,  nor  motion  at  the  ankle 
of  either  flexion  or  extension  could  be  detected.  The  foot, 
owing  to  gravity  effect,  was  in  the  position  of  equinus.  He 
certainly  seemed  a  fit  subject  for  one  of  the  numerous 
surgical  procedures  advised  for  flail  ankle.  Treatment 
by  various  measures  had  been  carried  out  continuously  for 
about  five  years.  The  foot  was  placed  in  a  splint  with 
the  foot-piece  at  right  angles,  the  back  of  the  splint  reaching 
to  the  upper  third  of  the  leg.  In  this  way  gravitational 
effect  was  overcome.  With  the  heel  supported  when  taken 
out  of  the  splint,  the  boy,  who  for  three  months  was  kept 
in  bed,  was  encouraged  many  times  daily  to  endeavour 
to  flex  or  extend  the  toes  and  foot,  attention  being  paid 
particularly  to  the  flexors  of  the  ankle. 

Though  at  first  this  was  without  apparent  result,  move- 
ment gradually  returned  in  the  toes,  and  in  six  months  a 
definite  tendo  achillis  could  be  felt.  The  extensor  action 
was  more  powerful  than  the  flexor,  and  although  the  foot- 
drop  had  lessened  there  was  still  little  power  over  flexion 
at  the  ankle  in  spite  of  twelve  months'  relaxation.  The 
deep  fascia  over  the  long  extensors  of  the  toes  and  of  the 
tibialis  anticus  was  removed  by  an  incision  over  the  front 
of  the  leg.  By  this  means  room  was  given  to  these  muscles 
for  expansion.  The  fascia,  to  which  they  are  closely 
attached,  is  frequently  found  contracted  down  on  them 
when  they  are  paralysed.  As  the  result  of  its  unyielding 
character  it  allows  no  room  for  their  expansion  when 
recovery  of  the  muscles  is  taking  place.  This  procedure 
was  followed  by  immediate  improvement  in  this  case,  so 
that  in  six  days  the  patient  was  not  only  able  to  flex  and 
extend  the  toes,  but  to  flex  the  ankle  almost  fully  as  well. 
A  soldier  who  had  his  great  sciatic  nerve  completely  severed 
(and  subsequently  repaired)  in  the  thigh  by  a  shell  wound 


THE    MUSCLES    OF   THE   TOES  197 

was  seen  six  months  afterwards.  With  three  months  of 
similar  treatment,  including  division  of  the  fascia,  though 
there  was  no  movement  in  either  foot  or  ankle,  there  was 
no  deformity  present,  and  the  patient  was  able,  when 
lying  down,  to  maintain  the  foot  at  a  right  angle  when 
it  was  lifted  off  the  bed,  and  could  walk  without  splint 
support. 

In  the  foot,  then,  the  important  thing  is  the  prevention 
of  deformity,  the  ideal  being  a  foot  at  a  right  angle.  When 
surgical  procedures  are  necessary,  such  as  division  or  length- 
ening of  tendons  or  tendon  transplantation,  we  have  to 
consider  in  connection  with  lateral  movements  of  the  foot 
that  there  is  inversion  and  eversion  in  both  the  flexed 
and  in  the  extended  position  of  the  foot.  Also  that  the 
two  inverters  and  the  two  everters  produce  their  own 
particular  action  only  when  the  foot  is  in  a  state  of  equili- 
brium as  regards  flexion  and  extension. 

It  is  in  connection  with  the  latter  position  that  the 
question  of  muscular  selection  comes  into  consideration. 
If  we  should  desire  to  weaken  inversion  or  eversion  which 
muscle  tendon  should  be  divided  ?  Numerous  types  of 
splints  have  been  devised  for  the  foot ;  they  are  only 
scientific  when  they  are  dominated  by  principles  of  muscle 
rest  and  muscular  action.  Where  we  wish  to  keep  the  foot 
at  a  right  angle  it  should  be  firmly  held  at  the  ankle  ; 
otherwise  in  a  few  hours  after  the  application  of  the  splint, 
the  heel  will  be  found  well  away  from  the  foot-piece,  fre- 
quently with  a  lateral  deviation  as  well. 

The  following  is  a  useful  form  of  foot  splint  which  can 
be  applied  for  equinus,  valgus,  or  varus,  and  the  foot-piece 
can  be  extended  for  calcaneus.  The  splint  is  made  of  tin 
in  two  pieces,  soldered  together  at  the  heel — one  for  the 
foot,  and  one  for  the  leg — the  latter  extending  to  the  junction 
of  the  middle  and  upper  third.  For  the  avoidance  of  pressure 
and  to  allow  for  the  play  of  an  ankle  strap  the  leg-piece  is 
opened  at  the  heel  (fig.  88) .  The  sole  of  the  foot  not  merely 
rests  against  the  foot-piece,  but  the  edges  of  the  latter  are 
turned  up  for  1  inch  on  the  inside  and  J  inch  on  the  outside, 


198  THE    ACTION    OF    MUSCLES 

thus  forming  lateral  shields  to  keep  the  foot  in  position. 
The  splint  is  lined  with  blanket  and  covered  with  chamois. 
The  extension  to  the  middle  of  the  thigh  (fig.  93,  p.  224)  is 
made  by  means  of  a  stem  of  malleable  iron  §  x  J  inch.  Two 
wings  are  attached  to  this  by  means  of  rivets — one  in  the 


Fig.  88. — A  useful  form  of  foot  splint.     The  arc  shoe. 

vicinity  of  the  knee  joint  and  one  at  the  upper  extremity 
in  the  thigh.  The  splint  is  attached  by  means  of  buckles 
and  webbing  straps.  The  ankle  strap,  in  a  case  of  in- 
version of  the  foot,  is  attached  to  the  lower  end  of  the 
leg-piece  on  the  outer  side.     By  means  of  the  opening  in 


THE    MUSCLES    OF   THE   TOES  199 

the  back  of  the  lower  end  of  the  leg-piece  it  is  brought 
up  on  the  outer  side  of  the  patient's  ankle,  across  the 
front  of  the  ankle,  and  descends  on  its  inner  side,  and 
passing  out  through  the  opening  is  attached  to  a  buckle 
on  the  inner  side  of  the  lower  end  of  the  leg-piece.  By 
means  of  this  attachment  a  constant  pressure  is  exerted 
on  the  outside  of  the  foot  so  as  to  favour  eversion.  The 
reverse  attachments  would  be  made  in  a  case  of  eversion 
of  the  foot. 


CHAPTER    XI 
MUSCLES    OF    THE    SPINE 

Arising  from  the  back  there  are  certain  muscles  concerned 
with  the  motion  of  the  upper  extremity  with  whose  move- 
ments they  have  been  described.  They  are  inserted  into 
the  humerus  or  scapula,  being  the  trapezius,  latissimus  dorsi, 
rhomboids,  and  levator  anguli  scapulae.  There  are  also 
muscles  arising  from  the  back  that  are  inserted  into  the 
ribs.  These  are  concerned  with  respiration.  They  include 
serratus  posticus  superior,  serratus  posticus  inferior,  and 
levatores  costarum,  and  will  be  described  under  the  mech- 
anism of  respiration.  The  muscles  of  the  back  may  be  con- 
veniently considered  under  three  groups,  viz.  : 
(i)  Those  which  move  the  head. 

(2)  Those  which  move  the  neck. 

(3)  Those  which  move  the  back  and  loins  (thoracic  and 

lumbar  spines). 

MUSCLES    WHICH    MOVE   THE    HEAD 

In  connection  with  the  movements  of  the  head  we  have 
to  consider  two  sets  of  articulations. 

(1)  Articulation  of  the  Atlas  with  the  Axis 

We  have  the  odontoid  process  of  the  axis  forming  an 
articulation  above  with  the  anterior  arch  of  the  atlas,  and 
below  with  the  transverse  ligament  on  which  it  is  supported. 
There  are  also  joints  on  either  side  between  the  articulatory 
surfaces  of  each  bone.     As  the  articulation  of  the  occiput 


MUSCLES    OF   THE    SPINE  201 

with  the  atlas  is  practically  a  pure  hinge  joint,  it  is  between 
the  atlas  and  axis  that  rotatory  movements  are  performed 
— the  atlas,  carrying  the  head  with  it,  moving  upon  the 
tooth-like  or  dentate  process  of  the  axis.  The  odontoid 
process,  by  means  of  which  rotation  of  the  head  is  rendered 
possible,  represents  the  separated  body  of  the  atlas  united 
with  that  of  the  axis.  It  is  found  persisting  as  an  inde- 
pendent bony  piece  in  reptilia,  for  example,  lizards,  and  also 
in  platypus. 


(2)  Articulation  of  the  Atlas  with  the  Occiput 

These  two  bones  are  connected  by  antero-posterior 
and  lateral  occipito-atlantal  ligaments.  The  two  upper 
articulatory  surfaces  of  the  atlas  are  somewhat  oval,  and 
hollowed  to  receive  the  condyles  of  the  occipital  bone.  By 
means  of  the  obliquity  of  each  component  forming  the  ar- 
ticulation rotatory  movements  are  prevented,  and  although 
slight  lateral  movement  is  permitted,  it  is  here  that  flexion 
and  extension  of  the  head  or  the  forward  and  backward 
nodding  movements  take  place.  The  axis  is  also  directly 
connected  to  the  occiput  by  the  occipito-axial  ligament 
and  the  odontoid  or  check  ligaments.  The  atlas  was 
so  called  owing  to  the  fact  that  it  supports  the  globe  or 
cranium,  and  the  axis  owing  to  the  tooth-like  (dentate) 
process  on  which  the  atlas  turns. 

The  movements  of  the  head  on  the  spine  are  : 

(1)  Flexion  and  extension  (bending  or  nodding  forwards, 
and  bending  or  nodding  backwards),  with  slight  lateral 
movement  to  one  or  other  side,  taking  place  between  the 
head  and  the  atlas. 

(2)  Rotatory  movements.  These  are  performed  by  the 
atlas  together  with  the  head  moving  on  the  odontoid  or 
tooth-like  process  of  the  axis  as  on  a  pivot. 

The  muscles  are  divided  into  two  main  groups — post- 
vertebral-dorsal,  or  extensors,  and  pre-vertebral-ventral,  or 
flexors. 


202  THE    ACTION    OF    MUSCLES 

(i)  Post- Vertebral,  or  Extending  Muscles 

There  are  on  each  side  : 

Splenius  capitis. 

Complexus. 

Trachelo-mastoid. 

Rectus  posticus  major. 

Rectus  posticus  minor. 

Superior  oblique. 

Inferior  oblique. 
The  last  four  muscles  form  the  boundaries  of  the  sub- 
occipital triangle. 

Splenius  Capitis.— The  splenius  was  so  named  because  it 
lies  like  a  surgical  splint  on  each  side  of  the  neck.  Though 
the  splenius  capitis  and  splenius  colli  are  usually  described 
together  owing  to  their  similar  origin,  they  are  two  distinct 
muscles,  capable  of  separate  dissection,  and  the  capitis  lies 
more  ventral  than  the  colli.  No  less  an  authority  than 
Albinus  made  the  distinction.  He  regarded  splenius 
capitis  as  that  part  arising  from  the  spines  of  the  vertebrae 
of  the  neck  and  inserted  into  the  cranium,  and  splenius 
colli  as  that  part  arising  from  the  dorsal  or  thoracic  vertebrae 
and  inserted  into  the  cervical  vertebrae.  This  muscle  arises 
from  the  lower  half  of  the  ligamentum  nuchae  and  spinous 
process  of  the  last  cervical  and  upper  five  or  six  dorsal 
vertebrae.  It  is  inserted  into  the  mastoid  process  of  the 
temporal  bone,  thus  obtaining  a  grip  well  forward  on  the 
skull,  and  also  into  the  lateral  part  of  the  superior  curved 
line  of  the  occipital  bone.  When  both  these  muscles  (splenii 
capitis)  act,  they  pull  the  head  directly  backwards  on  the 
atlas — extend  the  head  ;  when  one  acts  it  pulls  the  head 
obliquely  backwards  to  one  side. 

Complexus. — This  muscle  has  been  so  called  owing  to  the 
complexity  of  its  fleshy  and  tendinous  parts.  It  arises  by 
a  series  of  tendons  from  the  lower  four  cervical  and  the 
upper  six  or  seven  dorsal  or  thoracic  vertebrae.  The  thick 
fleshy  belly,  partly  tendinous  and  partly  muscular,  filling  up 
the  hollow  at  the  sides  of  the  cervical  vertebrae  is  inserted 


SPLENIUS 
CAPITIS 


TRACHE.L.0 
MASTOID 


SUPER:  OBLiQ: 
RECT:  POST:  MINOR 
"rECT:  POST-  MAJOR 
INPER  :  OBLIQ: 

COM  PLEXUS 

31  VENTER    CERVICIS 


SPINALIS    DORSI 


LONQISSIMUS 
DORSI 


L.UMBALIS 


ERECTOR   SPIN^E 


Fig.  89.— The  extenders  (dorsi  flexors)  of  the  head.     The  erector 
spinae  and  its  divisions. 


202] 


MUSCLES    OF   THE    SPINE  203 

into  the  occipital  bone  between  the  superior  and  inferior 
curved  lines.  Albinus  regarded  the  inner  part  of  the 
muscle,  which  is  fleshy  above  and  below  and  tendinous 
centrally,  as  a  distinct  portion,  under  the  name  biventer 
cervicis.  It  is  best  to  regard  it,  however,  as  the  inner 
part  of  the  complexus.  When  both  complexi  act  they 
extend  the  head,  draw  it  backwards  and  so  assist  the 
splenii ;  when  one  acts  the  head  is  drawn  obliquely  back- 
wards, to  one  side.  Thus,  both  the  splenii  and  complexi 
are  important  factors  in  maintaining  the  head  erect. 

Trachelo-Mastoid. — This  small  muscle,  so  called  owing 
to  its  origin  in  the  neck  and  insertion  into  the  mastoid,  has 
also,  owing  to  the  mixture  of  tendon  and  muscle  in  its  belly, 
been  called  the  complexus  minor.  It  arises  by  separate 
tendons  from  the  lower  cervical  and  six  upper  thoracic 
vertebrae,  and  is  inserted  into  the  mastoid  process  of  the 
temporal  bone  beneath  the  splenius.  Its  use  is  like  that  of 
the  complexus  and  splenius.  When  one  acts  the  head  is 
drawn  backwards  obliquely  to  one  side  ;  when  both  act 
the  head  is  extended  or  drawn  directly  backwards. 

Rectus  Posticus  Major. — This  muscle  passes  upwards 
and  outwards  on  each  side  from  the  spine  of  the  axis  to 
the  inferior  curved  line  of  the  occipital  bone  and  adjacent 
surface  of  bone  below  it. 

Rectus  Posticus  Minor. — This  muscle  passes  on  each  side 
from  the  tubercle  or  spine  of  the  atlas  to  the  occipital  bone 
below  the  inferior  curved  line,  and  internal  to  the  preceding. 
When  the  muscles  of  the  two  sides  act  the  recti  postici  pull 
the  head  directly  backwards  (extend)  on  the  atlas  ;  when 
one  acts  it  draws  the  head  obliquely  backwards  to  its 
own  side.  Older  anatomists  called  the  smaller  posterior 
recti,  passing  from  the  atlas  to  the  head,  the  renuentes 
or  backward  nodders,  in  opposition  to  the  small  anterior 
recti,  which  were  called  annuentes  or  forward  nodders  of  the 
head. 

Superior  Oblique. — This  arises  from  the  upper  surface  of 
the  transverse  process  of  the  atlas,  and  passing  upwards  and 
inwards  is  inserted  into  the  occipital  bone  between  the  two 


204  THE    ACTION    OF    MUSCLES 

curved  lines.  In  spite  of  their  name  these  muscles  do  not, 
as  might  be  imagined,  rotate  the  head  on  the  atlas.  This 
movement  is  not  permitted  at  this  articulation.  Acting 
together  these  muscles  draw  the  head  directly  backward 
on  the  atlas  ;  acting  singly  the  head  is  drawn  obliquely 
to  one  or  other  side. 

Inferior  Oblique. — This  muscle,  passing  between  two 
vertebrae,  is  not  a  direct  muscle  acting  on  the  head,  although 
through  its  action  rotation  of  the  head  is  possible.  It 
passes  outwards  on  each  side,  from  the  spine  of  the  axis 
to  the  projecting  transverse  process  of  the  atlas,  by  means 
of  which  great  leverage  power  is  obtained.  When  the 
muscle  of  one  side  acts,  the  other — its  opponent — is  in  a 
state  of  relaxation  and  elongation.  The  result  of  contrac- 
tion is  to  rotate  or  roll  the  atlas  round  the  odontoid  process 
of  the  axis,  so  that  the  transverse  process  of  the  atlas  is 
moved  towards  the  spine  of  the  axis.  As  apart  from 
ligaments  there  is  a  direct  muscular  connection  between 
the  atlas  and  cranium,  it  follows  that  the  head,  whether  in 
the  state  of  flexion  on  the  atlas  or  extension,  is  also  rotated 
with  the  atlas  on  the  odontoid  process  of  the  axis,  and  the 
face  turned  to  the  same  side. 


(2)  Pre- Vertebral  or  Bending  Muscles 

These  are  on  each  side  (fig.  90). 

Rectus  capitis  anticus  major,  or  longus  capitis. 
Rectus  capitis  anticus  minor. 
Rectus  lateralis. 
Sterno-mastoid. 
Rectus  Capitis  Anticus  Major. — This  arises  from  the 
front  of  the  transverse  processes  of  the  third,  fourth,  fifth, 
and  sixth  cervical  vertebrae,  and  is  inserted  on  each  side 
into  the  basilar  process  of  the  occipital  bone. 

Rectus  Capitis  Anticus  Minor. — This  small  muscle  lies 

beneath  the  preceding,  and  passes  from  the  atlas  to  the 

basilar  process  of  the  occipital  bone,  dorsal  to  the  preceding. 

Rectus   Lateralis. — This  muscle  arises  from  the  trans- 


MUSCLES    OF   THE    SPINE  205 

verse  process  of  the  atlas,  and  is  inserted  into  the  jugular 
process  of  the  occipital  bone.  These  muscles  are  the 
benders  of  the  head  on  the  atlas,  flexing  the  head  directly 
forwards  when  both  sides  act,  or  bending  it  obliquely  to 
one  side  when  only  one  muscle  acts.  They  may  be  desig 
nated  flexores  capitis. 

Sterno-Mastoid. — This  muscle,  passing  obliquely  across 
the  side  of  the  neck,  is  probably  the  most  prominent  in  the 
body.  It  arises  at  the  lower  part  of  the  neck  from  the 
first  part  of  the  sternum  and  inner  third  of  the  clavicle, 
and  is  inserted  above  into  the  mastoid  process  of  the  tem- 
poral bone  and  the  superior  curved  line  of  the  occipital 
bone.  When  both  sterno-mastoids  act  they  flex  the  head  on 
the  atlas,  and  by  their  aid  the  chin  can  be  brought  down  to 
the  chest.  Their  action  is  especially  seen  when  we  raise  the 
head  from  the  body  in  the  recumbent  position.  When  only 
one  sterno-mastoid  acts  it  bends  the  head  obliquely  down- 
wards towards  the  shoulder  of  the  same  side.  This  muscle, 
when  it  contracts,  does  not  rotate  the  head  so  as  to  carry 
the  face  towards  the  opposite  side.  Its  fulcrum  or  centre  of 
motion  is  the  articulation  between  the  occiput  and  the  uppei 
surface  of  the  atlas,  and  rotation  does  not  take  place  at 
this  articulation.  The  movements  of  flexion  and  extension 
at  the  articulation  between  the  atlas  and  the  occiput  repre- 
sent a  striking  example  of  the  first  order  of  leverage.  Thus, 
in  backward  movement  of  the  head,  the  dorsal  or  extending 
muscles  represent  the  power,  the  front  of  the  head  represents 
the  weight  to  be  raised,  and  between  the  power  and  weight 
is  the  fulcrum,  or  centre  of  motion,  at  the  occipito-atlantal 
articulation. 


CHAPTER    XII 
MUSCLES    WHICH    MOVE    THE    NECK 

While  the  preceding  muscles  move  the  head  together  with 
the  atlas  or  first  vertebra  only,  the  remaining  vertebrae  of 
the  neck  remaining  unmoved,  the  following  muscles  act 
directly  on  the  vertebrae  of  the  neck,  and  so  move  the  head 
indirectly.  The  former  are  the  proper  muscles  of  the  head, 
and  the  latter  the  common.  Flexion  and  extension  move- 
ments are  free  in  the  cervical  region.  These  movements 
are  also  free  in  the  lumbar  region ;  but  while  extension  is 
most  free  in  the  cervical,  flexion  is  most  free  in  the  lower 
lumbar  region.  In  addition,  lateral  movements  and  slight 
rotation  are  permitted.  Speaking  generally,  the  greatest 
mobility  of  the  spine  is  in  the  cervical  region.  This  is 
allowable  owing  to  the  thickness  of  the  fibro-cartilage  per- 
mitting of  a  large  amount  of  elasticity,  small  size  of  the 
vertebrae,  horizontal  position  of  the  short  spinous  processes, 
and  the  oblique  direction  of  the  articulations.  The  muscles 
acting  on  the  cervical  vertebrae  may  be  divided  into  two 
main  groups  : 

(i)  Dorsal — post-vertebral — or  extensors. 

(2)  Ventral — pre-vertebral — or  flexors. 

(1)  Dorsal — Post- Vertebral — or  Extending 
Muscles 
These  are : 

Splenius  cervicis  or  colli. 

Costalis    cervicis     (cervicalis    ascendens,     ilio-costalis 

cervicis) . 
Transversalis  cervicis  (longissimus  cervicis). 

206 


MUSCLES    WHICH    MOVE   THE    NECK       207 

These  latter  muscles  have  been  regarded  as  continuations 
of  the  main  divisions  of  the  erector  spinae,  and  named  accord- 
ingly. It  would  be  better  to  dissociate  them  from  the 
muscles  of  the  loins,  as  they  are  distinct  muscles  with  distinct 
functions. 

In  addition  to  these  three  muscles  we  have  in  the  cervical 
region — as  in  the  dorsal  and  lumbar  regions — innumerable 
and  intricate  small  muscles  rilling  up  the  hollows  and 
interstices  on  the  back  of  the  spine  on  each  side.  These, 
from  their  dispositions,  are  called  semi-spinales,  multifidus 
spinae,  inter-transversales,  and  inter-spinales. 

Splenius  Cervicus. — This  arises  on  each  side,  in  common 
with  the  splenius  capitis,  from  the  ligamentum  nuchae  and 
the  spinous  processes  of  the  last  cervical  and  upper  six 
dorsal  vertebrae,  and  is  inserted  into  the  transverse  pro- 
cesses of  the  three  upper  cervical  vertebrae.  When  both 
these  muscles  act  they  draw  directly  backwards  or  extend 
the  upper  cervical  vertebrae  ;  when  only  one  acts  the  upper 
vertebrae  are  drawn  obliquely  backwards  to  one  side,  by 
which  movement  the  head  is  directed  towards  the  opposite 
shoulder. 

Costalis  Cervicis. — This  arises  on  each  side  from  the 
angles  of  the  upper  six  ribs,  and  is  inserted  by  a  series  of 
narrow  tendons  into  the  transverse  processes  of  the  fourth, 
fifth,  and  sixth  cervical  vertebrae. 

Trans versalis  Cervicis. — This  arises  on  each  side  from 
the  transverse  processes  of  the  upper  six  dorsal  or  thoracic 
vertebrae,  and  is  inserted  into  the  transverse  processes  of 
second,  third,  fourth,  fifth,  and  sixth  cervical  vertebrae. 

These  two  muscles  are,  like  the  preceding,  extensors  of 
the  cervical  vertebrae,  helping  to  keep  the  neck  erect.  If 
either  acts  alone  the  cervical  vertebrae  are  drawn  obliquely 
backwards. 

Semi-spinales. — These  partly  tendinous  muscles,  one  set 
on  each  side,  were  so  called  as  belonging  half  to  the  trans- 
verse and  half  to  the  spinous  processes  of  the  vertebrae. 
They  are  met  with  in  connection  with  the  movement  of 
both  the  dorsal  and  cervical  spine.     Those  for  the  move- 


208  THE   ACTION    OF   MUSCLES 

ment  of  the  cervical  vertebrae  arise  on  each  side  from  the 
transverse  processes  of  the  upper  six  thoracic  (dorsal) 
vertebrae,  and  are  inserted  into  the  spinous  processes  of  all 
the  cervical  vertebrae  except  the  atlas.  When  the  muscles 
of  the  two  sides  act  they  draw  the  cervical  vertebrae,  except 
the  atlas,  directly  backwards,  and  so  help  to  extend  the  neck. 
When  those  of  one  side  act  only,  they  undoubtedly,  from 
the  obliquity  of  their  direction,  cause  rotation  of  the  cervical 
vertebrae  and  indirectly  of  the  head.  By  means  of  the 
inferior  oblique  muscles,  which  pull  in  an  opposite  direction, 
the  short  and  rapid  turnings  of  the  head  are  probably 
carried  out. 

Multifidus  Spinae. — Unlike  the  semi-spinales  these 
muscles  are  more  marked  below  than  above.  The  multifidus 
lies  along  the  hollow  of  the  back  on  each  side  of  the  spinous 
processes,  and  is  found  in  the  loins,  back,  and  cervical 
region.  It  was  split  up  formerly  by  anatomists  into 
numerous  divisions,  but  these  are  so  connected  that  they 
have  been  described  under  a  single  name,  "multifidus  spinae." 
In  the  cervical  region  the  muscular  bundles  are  inserted 
into  the  spines  of  all  the  vertebrae  except  the  atlas  :  those 
for  the  lower  cervical  vertebrae  arising  from  the  transverse 
processes  of  the  upper  thoracic  vertebrae,  and  those  for 
the  upper  cervical  vertebrae  arising  from  the  articular 
processes  of  the  four  lower  cervical  vertebrae.  In  the 
neck  the  multifidus  fibres  resemble  in  action  those  of  the 
semi-spinales.  When  those  of  the  two  sides  act  they  draw 
the  cervical  vertebrae,  except  the  atlas,  directly  backwards, 
and  so  help  to  extend  the  neck  ;  when  those  of  one  side 
act  they  cause  rotation  of  the  cervical  vertebrae,  and  so 
indirectly  of  the  head. 

Inter-transversales. — These  small  slips  extend  between 
the  transverse  processes  of  the  spine.  They  are  best 
developed  in  the  cervical  region,  where  they  are  double, 
owing  to  the  fact  that  lateral  motion  in  the  neck  is  possible, 
and  the  transverse  processes  forked.  They  extend  from 
the  atlas  (between  it  and  the  axis)  to  the  seventh  cervical, 
and  the  bundles  are  most  numerous  where  movement  is 


MUSCLES    WHICH   MOVE   THE   NECK       209 

most  marked,  namely  between  the  atlas  and  axis.  When  the 
muscles  of  one  side  act,  these  fibres,  by  approximating  the 
transverse  processes,  produce  some  lateral  movement  in 
the  cervical  vertebrae,  bending  them  to  the  one  side  ;  when 
both  act  they  help  to  maintain  the  erect  position  of  the  neck. 
Inter-spinales. — These  are  short  muscular  bundles,  most 
marked  in  the  cervical  region  where  movement  is  best, 
extending  between  the  spinous  processes  of  the  vertebrae. 
They  were  first  discovered  by  Cowper  in  1690.  When  they 
contract  they  draw  the  spines  of  the  vertebrae  of  the  neck 
nearer,  and  so  help  to  extend  the  cervical  spine. 

(2)  Ventral — Pre-Vertebral — or  Flexing 
Muscles 

They  are  : 

Longus  colli.  \  See  fig.  90, 

Three  scaleni :  anticus,  medius,  and  posticus-  J    p.  210. 

Longus  Colli. — This  long  flat  muscle,  which  lies  on  each 
side  on  the  front  of  the  cervical  vertebrae,  extends  from 
within  the  thorax  below  to  the  atlas  above.  Three  parts 
are  recognized :  Superior  oblique  portion  passing  from 
the  transverse  processes  of  the  third,  fourth,  and  fifth 
cervical  vertebrae  upwards  and  inwards  to  the  tubercle 
on  the  front  of  the  atlas.  Vertical  portion  passing  from  the 
front  of  the  bodies  of  the  upper  three  thoracic  and  lower 
three  cervical  vertebrae  to  the  front  of  the  second,  third, 
and  fourth  cervical  vertebrae.  Inferior  oblique  portion 
passing  up  and  out  from  the  upper  three  thoracic  vertebrae 
to  the  transverse  processes  of  the  fifth  and  sixth  cervical 
vertebrae.  By  means  of  the  division  of  this  muscle  into 
three  portions  added  strength  is  given  to  its  contraction. 
When  it  acts  with  its  fellow  of  the  opposite  side  it  bends 
the  cervical  spine  forwards,  and  so  indirectly  the  head ; 
when  the  muscle  of  one  side  acts  the  cervical  spine  is  bent 
laterally  to  one  side. 

Scaleni. — These  muscles  were  so  called  owing  to  their 
resemblance  collectively  on  each  side  to  a  scalene  triangle. 
14 


210 


THE   ACTION    OF   MUSCLES 


The  true  anatomy  is  to  regard  the  scalenus  anticus,  medius, 
and  posticus  as  one  flat  triangular  muscle  extending  from 

RECT:  CAP:  ANT.  M/NOR 


RECT.CAP:  ANT.  MAJOR 


SCALENUS  ANT 


RECTUS  LATERALIS 
SCALENUS  MED /US 

LONGUS  COLLI 

CALENUS  POST: 


QUADRATUS 
LUMBORUM 


Fig.  90. — The  benders  (with  gravity)  of  the  head  and  spine. 

the  first  and  second  ribs  below  to  the  transverse  processes 
of  the  six  lower  cervical  vertebrae  above.     It  is  usually, 


MUSCLES    WHICH    MOVE   THE   NECK       211 

however,  described  in  three  portions  on  each  side,  though 
Winslow  described  but  two,  Douglas  four  portions,  and 
Albinus  no  less  than  five  portions. 

The  Anticus  passes  from  the  scalene  tubercle  on  the 
inner  part  of  the  upper  surface  of  the  first  rib  near  the 
cartilage,  almost  vertically  upwards  to  the  transverse 
processes  of  the  third,  fourth,  fifth,  and  sixth  cervical  verte- 
brae ;  the  Middle  passes  between  the  upper  surface  of  the 
first  rib  dorsal  to  the  anticus  and  the  transverse  processes 
of  the  lower  six  cervical  vertebrae  ;  and  the  Posticus  passes 
between  the  upper  edge  of  the  second  rib  near  the  spine 
to  the  transverse  processes  of  the  lower  three  cervical 
vertebrae . 

As  regards  the  action  of  the  scaleni  muscles,  discussion 
is  always  raised  as  to  whether  they  are  flexors  of  the  neck 
primarily  and  muscles  of  inspiration  secondarily,  or  in- 
spiratory primarily  and  flexors  secondarily.  It  seems  to  be 
generally  agreed  that  when  the  fixed  point  is  below  these 
muscles  flex  the  cervical  spine,  and  when  the  fixed  point 
is  above  they  elevate  the  first  two  ribs  and  are  muscles  of 
inspiration.  Of  one  thing,  however,  we  can  be  certain  : 
they  are  either  muscles  of  respiration  or  flexors  of  the  cervical 
spine,  but  they  are  not  both.  We  must  refer  the  fulcrum 
or  centre  of  motion  either  to  the  ribs  or  to  the  vertebrae, 
not  to  both.  The  scalenes  have  not  two  separate  fulcra 
or  centres  for  action. 

We  would  first  observe  that  though  there  are  powerful 
muscles  on  the  back  of  neck  acting  as  cervical  extenders, 
yet  antagonizing  these  so  far  we  have  only  described  one 
muscle,  the  longus  colli.  At  once  it  may  be  argued  that 
the  action  of  the  longus  colli  is  favoured  by  gravity  ;  in  other 
words,  that  an  effort  is  required  to  hold  the  neck  extended 
and  the  head  erect.  If  we  are  recumbent,  however,  some- 
thing more  powerful  is  needed  to  flex  the  extended  neck 
than  the  longus  colli.  Again,  should  the  origin  of  these 
muscles  be  at  the  spine,  there  would  be  no  particular 
reason  for  the  multiform  origin  from  all  the  cervical 
vertebrae  except  the  atlas,  in  order  to  secure  an  action 


212  THE   ACTION    OF   MUSCLES 

on  the  first  two  ribs.  On  the  other  hand,  acting  from 
below,  a  strong  grip  is  secured  by  this  multiple  attachment 
in  flexing  the  cervical  spine.  Furthermore,  the  attach- 
ment to  elastic  ribs — elastic  owing  to  the  interposition  of 
cartilage  between  them  and  the  sternum — would  rather 
strengthen  than  weaken  muscular  pull  on  the  vertebrae. 

The  scaleni,  acting  together,  bend  the  cervical  spine 
directly  forwards,  assisting  the  longus  colli.  When  those  of 
one  side  only  act  the  cervical  spine  is  bent  to  one  or  the  other 
side.  In  this  action  they  are  more  powerful  than  the  muscles 
longus  colli,  though  in  the  former  action  the  longus  colli, 
from  their  median  position,  are  the  more  powerful.  Should 
the  fixed  point  for  the  action  of  these  muscles  be  above, 
they  would  flex  the  trunk  at  the  cervico-dorsal  junction  of 
the  spine.  This  requires  much  practice,  though  I  have 
frequently  seen  it  performed  by  acrobats  and  jugglers  when 
lying  on  the  back  with  the  head  and  neck  fixed. 

As  regards  lateral  movement  of  the  cervical  spine,  and 
indirectly  of  the  head,  this  is  performed  by  the  combined 
action  of  the  muscles  of  one  or  other  side — the  actions  of 
the  two  groups  on  the  front  and  back  being,  as  regards 
flexion  and  extension  of  the  neck,  in  a  state  of  equilibrium  : 
the  cervical  spine  is  neither  dorsi-flexed  nor  ventro-flexed. 
In  this  position  lateral  movement  is  best  performed.  Should 
we,  however,  dorsi-flex  (hyper-extend)  or  ventro-flex  (hyper- 
flex)  lateral  movement  is  greatly  impaired,  especially  in  the 
former  position,  although  rotatory  movements  can  be  made. 
In  other  words,  with  hyper-flexion  or  hyper-extension  one 
set  of  muscles  is  contracted,  and  the  other  relaxed  and 
elongated.  In  the  mid  state,  or  state  of  equilibrium  as 
regards  flexion  and  extension,  contraction  of  one  side  with 
lateral  movement  is  possible,  owing  to  relaxation  and 
elongation  of  those  of  the  opposite  side. 


CHAPTER    XIII 

MUSCLES  WHICH  MOVE  THE  BACK  AND  LOINS 
(THORACIC    AND    LUMBAR    REGIONS) 

In  the  thoracic  (dorsal)  region  of  the  spine  flexion  and 
extension  reach  their  minimum  especially  in  the  upper  half, 
and  in  the  middle  of  the  back  scarcely  any  motion  is  per- 
mitted at  all.  In  the  lumbar  region  these  movements  are 
free,  especially  in  the  lower  portion.  Flexion  movement  in 
the  spine  is  probably  greatest  between  the  fourth  and 
fifth  lumbar  vertebrae.  The  small  mobility  in  the  dorsal 
region  is  associated  with  the  vertical  direction  of  the  articular 
processes,  the  small  amount  of  inter-vertebral  substance 
compared  with  the  lumbar  region,  and  the  over-lapping 
of  the  spinous  processes. 

As  a  result  the  thoracic  spine  becomes  a  more  or  less 
fixed  point  for  the  attachment  of  muscles  acting  on  the 
neck  as  well  as  for  the  action  of  the  intercostal  muscles, 
since  the  centre  of  motion  of  the  ribs  is  at  the  spine.  In  the 
thoracic  region,  in  the  upper  half  rotation  can  take  place, 
but  not  in  the  lower  part.  Rotation  is  absent  in  the  lumbar 
region,  but  here  lateral  motion  can  take  place.  The  motion 
between  individual  vertebrae  is  limited,  but  in  the  whole 
spine  collectively  it  becomes  a  very  appreciable  amount.  By 
means  of  the  curves  in  the  cervical,  thoracic,  lumbar,  and 
sacral  regions,  the  spine  is  enabled  to  yield  to  pressure  in  the 
direction  of  these  curves,  and  so  to  break  shocks  in  violent 
motions  of  the  body  ;  this  would  be  impossible  were  the 
spine  a  perpendicular  structure,  by  which  its  elasticity  would 
be  lost.  This  elasticity  is  also  effected  by  means  of  the 
spinal  column  consisting  of  a  number  of  small  bones  instead 

213 


214  THE    ACTION    OF    MUSCLES 

of  one  unyielding  bone  for  the  protection  of  the  spinal  cord. 
Not  merely  must  the  cord  be  protected,  but  the  spine  must 
accommodate  itself  by  its  flexibility  to  the  motions  of  the 
body,  which  it  is  enabled  to  do  by  means  of  a  multiplicity 
of  joints. 

The  muscles  in  this  region  may  be  primarily  divided, 
as  in  the  cervical  region,  into  two  divisions,  posterior  or 
dorso-vertebral  for  extension,  and  anterior  or  pre-vertebral 
for  flexion. 


I.  Dorso- Vertebral  or  Extending  Muscles 

These  are  on  each  side 

Erector  spinae  and  its  three  divisions : 
Ilio-costalis. 
Longissimus  dor  si. 
Spinalis  dor  si. 

In  addition,  as  in  the  cervical  region,  we  have  innumerable 
and  intricate  small  muscles  filling  up  the  hollows  and  inter- 
stices on  the  back  of  the  spine  on  each  side.  These,  from 
their  disposition,  are  called  semi-spinales,  multifidus  spinae, 
rotatores,  inter-transversales,  and  inter-spinales. 

Erector  Spinae. — This  is  the  mass,  partly  muscular  and 
partly  tendinous,  placed  at  the  root  of  the  spine  dorsally 
on  each  side.  It  is  attached  to  the  back  of  the  crest  of  the 
ilium,  posterior  sacro-iliac  ligament,  back  of  the  sacrum, 
and  the  spines  of  the  lumbar  vertebrae.  From  this  muscle 
three  columns  arise,  outer  or  ilio-costalis,  middle  or  longis- 
simus dorsi,  and  inner  or  spinalis  dorsi  (fig.  89,  p.  202). 

Ilio-Costalis. — This  passes  up  and  outwards  on  the  back 
of  the  chest  wall  and  is  inserted  into  the  angles  of  the  lower 
six  ribs.  This  small  muscle,  little  more  than  a  muscular 
ligament  (accessorius  or  ilio-costalis  dorsi),  passing  from  the 
lower  six  to  the  upper  six  ribs  would  appear  in  man  to  be 
little  more  than  an  ancestral  relic. 

Longissimus  Dorsi. — -This  is  the  main  division  of  the 
erector  spinae,  and  has  an  attachment  to  the  transverse 


WHICH    MOVE    THE    BACK    AND    LOINS      215 

process  of  the  lumbar  vertebrae.  It  has  a  double  set  of 
insertions,  viz.  to  the  transverse  process  of  the  thoracic 
vertebrae  and  also  into  the  back  of  all  the  ribs,  so  that  it 
has  an  extensive  grip  for  extension. 

Spinalis  Dorsi.— This  is  so  called  because  it  is  entirely 
attached  to  spinous  processes.  It  does  not  pass  to  the 
neck.  It  arises  from  the  spines  of  the  lumbar  and  lower 
two  thoracic  or  dorsal  vertebrae  and  is  inserted  into  the 
spines  of  the  upper  thoracic  vertebrae. 

Semi-spinalis. — So  called  on  account  of  belonging  partly 
to  transverse  and  partly  to  spinous  processes  of  the  vertebrae  ; 
it  passes  on  each  side  from  the  transverse  processes  of  the 
lower  six  thoracic  vertebrae  to  the  spinous  processes  of  the 
four  upper  ones. 

Multifldus  Spinse. — These  are  not  only  present  in  the 
cervical  region  as  described,  but  in  the  thoracic,  lumbar, 
and  sacral  regions  as  well.  In  the  lumbar  regions  they  arise 
from  the  articular  processes  and  in  the  thoracic  region  from 
the  transverse  processes,  and  are  inserted  into  the  spinous 
processes  of  the  vertebrae  above,  some  of  the  fibres  passing 
between  adjacent  vertebrae,  others  to  second,  third,  or 
fourth  vertebrae  above. 

Inter-spinales. — These  short  muscles  bundles  between 
the  spinous  processes  of  adjacent  vertebrae  are,  as  stated, 
well  developed  in  the  cervical  region,  are  almost  entirely 
wanting  in  the  thoracic  spine,  where  the  vertebrae  are 
almost  fixed  except  at  upper  and  lower  parts,  and  are 
found  again  in  the  lumbar  region. 

Rotatores  Spinae. — These  are  found  only  in  connection 
with  the  thoracic  (dorsal)  spine,  and  extend  on  each  side 
between  the  transverse  process  of  one  vertebra  and  the 
lamina  of  the  vertebra  above. 

Inter-transversales. — These  extend  between  adjacent 
transverse  processes  of  the  vertebrae.  Like  the  inter- 
spinales  they  are  almost  absent  in  the  thoracic  spine,  except 
below  and  above,  but  in  the  lumbar  region  they  are  well 
developed  for  the  lateral  or  twisting  movements  of  this 
part. 


2l6 


THE    ACTION    OF    MUSCLES 


Action  of  the  Dorsal  Muscles 

The  Erector  Spinae  and  its  divisions  act  as  extenders  of 
the  spine,  serving  to  maintain  the  spine  erect  and  so  counter- 
acting the  tendency  of  the  body  to  fall  forwards.  Its 
power  is  increased  owing  to  the  extensive  arborisations  of 


EXTENDERS 
Or  KNEE 


EL.EXORS 
Or  KNEE 


rLEXORS 
Of  ANKLE. 


EXTENDERS 
OF     ANKLE 


Fig.  91. — Flexion  of  the  rigid  body  at  the  knee  joint. 

its  insertions.  As  stated,  there  is  a  comparative  absence 
of  forward  or  backward  movement  of  the  thoracic  spine, 
and  the  chief  movement  is  in  the  lumbar  joints,  and  especi- 
ally at  the  junction  of  the  thoracic  and  lumbar  curves  of 
the  spine.  When  the  muscles  of  the  one  side  act  the 
spine  is  drawn  backwards  to  one  or  other  side.  An  extreme 
instance  of  the  action  of  the  erectores  spinae  is  seen  in 
acrobats,  who,  standing  erect,  are  enabled  to  throw  their 


WHICH    MOVE   THE    BACK    AND    LOINS     217 

heads  backwards  and  drink  from  a  glass  of  water  placed  on 
the  floor.  Here  we  have  at  first  a  condition  of  hyper- 
extension  (dorsi-flexion)  of  the  head  and  at  the  loins,  and, 
with  the  spine  thus  fixed,  the  flexors  of  the  knee,  with  the 
legs  and  feet  as  fixed  points,  flex  the  trunk  and  thigh  on 
the  leg  at  the  knee  joint  (fig.  91).  I  have  never  seen  this 
done  as  a  pure  back  extension  movement,  and  I  doubt 
whether  such  a  movement  is  possible. 

The  Semi-spinales  are  not  found  in  the  lumbar  region. 
When  the  muscles  of  one  side  act  they  cause,  owing  to  the 
obliquity  of  their  direction,  rotation  of  the  thoracic  vertebrae  ; 
and  as  these  muscles  act  similarly  on  the  cervical  spines 
the  body  is  turned  to  the  opposite  side.  Acting  together 
they  help  to  support  the  spine  against  gravity. 

The  Multifidus  Spinse. — In  the  thoracic  region  both 
sets,  acting  together,  help  to  prevent  the  spine  being  bent 
forward  by  gravity.  When  the  muscles  of  one  side  act 
rotation  of  the  vertebrae  is  produced  and  the  trunk  is 
turned  to  the  opposite  side. 

In  the  lumbar  region  extension  is  produced  when  the 
muscles  of  the  two  sides  act,  and  lateral  movement  when 
the  muscles  of  one  side  only  act. 

The  Inter-spinales  approximate  the  spines  of  the  lumbar 
vertebrae,  and  so  help  extension. 

Rotatores. — These  assist  the  multifidus  and  semi-spinales 
muscles  of  the  same  side,  so  as  to  rotate  the  dorsal  vertebrae 
and  turn  the  trunk  to  the  opposite  side. 

The  Inter-transversales  are  well  developed  in  the 
lumbar  region,  and,  by  approximating  the  transverse 
processes,  produce  the  lateral  or  twisting  movement  which 
is  found  in  this  portion  of  the  spine. 

II.    Anterior  or  Pre-Vertebral  Muscle   (Quadratus 

Lumborum) 
It  is  interesting  to  note  that  there  is  no  pre-vertebral 
muscle  in  the  thoracic  region  of  the  spine,  where  flexion 
and  extension  are  practically  absent.     Extending  force  in 
that  region  must  be  exerted  chiefly  against  gravity. 


218  THE    ACTION    OF    MUSCLES 

Quadratus  Lumborum. — This  muscle,  called  quadratus 
owing  to  its  somewhat  square  shape,  forms  part  of  the  dorsal 
wall  of  the  abdomen,  and  extends  between  the  iliac  crest  and 
the  last  rib  (fig.  90,  p.  210).  It  arises  below  from  the  dorsal 
part  of  the  crest  of  the  ilium  for  about  two  inches,  and  from 
the  ligaments  connecting  the  back  of  the  ilium  to  the  sacrum 
and  to  the  lumbar  vertebrae.  As  it  ascends  ventral  to  the 
lumbar  vertebrae  it  sends  tendinous  slips  into  the  transverse 
processes  of  the  four  upper  ones.  In  addition,  it  secures  an 
attachment  to  the  lower  edge  of  the  last  rib,  and  a  small 
process  is  traced  beneath  the  arch  of  the  diaphragm,  to  be 
inserted  into  the  body  or  ventral  part  of  the  last  thoracic 
vertebra.  When  the  muscles  of  both  sides  act  they  flex 
the  spine  at  the  lumbar  vertebrae,  and  so  are  the  physio- 
logical antagonists  of  the  erectores  spinae  ;  when  the 
muscle  of  one  side  acts  the  spine  is  bent  towards  the  same 
side.  When  the  psoas  minor,  which  extends  from  the  side 
of  the  first  lumbar  vertebrae  to  the  ilio-pectineal  line  of  the 
pelvis,  is  present,  it  would  act  as  a  flexor  and  assist  the 
quadratus  lumborum. 

Should  the  dorsal  and  cervical  spines  be  fixed,  as  when, 
for  example,  an  acrobat  lies  on  his  back,  contraction  of  the 
quadratus  results  in  flexion  of  the  sacrum,  pelvis,  and  so 
of  the  lower  limbs  at  the  lumbar  joints.  Contraction  of  the 
erectores  spinae,  when  an  acrobat  is  lying  prone,  will  similarly 
produce  extension  at  these  joints.  Thus,  the  quadratus  is 
an  important  factor  in  maintaining  spinal  equilibrium. 
We  cannot  help  being  struck  by  the  paucity  of  muscular 
engines  on  the  front  of  the  spine  for  the  purposes  of 
flexion,  compared  with  the  multiplicity  of  muscles  which 
subserve  the  function  of  extension,  i.e.  erection  of  the 
head,  neck,  and  back.  Apart  from  neutralizing  their 
antagonists  these  dorsal  muscles  are  constantly  fighting 
gravity  when  we  either  stand  or  sit.  These  many  and 
strong  muscles  are  important  factors  in  preventing  the 
body  from  falling  forwards,  to  which  there  is  a  continual 
liability — a  liability  increased  by  the  projection  forwards 
from  the  spine  of  the  head  as  well  as  the  thorax.     When 


WHICH    MOVE   THE    BACK    AND    LOINS     219 

we  stand  motionless  these  muscles  are,  we  must  remember, 
actively  contracted.  There  is  no  such  state  as  skeletal 
balance  apart  from  muscular  action. 

Pelvic  Tilting 

As  stated,  lateral  movement  is  free  at  the  lumbar  region  ; 
when  standing  we  can  roll  the  trunk  from  one  side  to 
the  other  on  the  pelvis  and  lower  limbs,  so  as  to  bring  the 
lumbar  vertebrae  nearer  to  the  os  ilium.  Just  as  in  the 
cervical  region,  when  this  motion  is  permitted,  the  muscles 
producing  flexion  and  extension  at  this  region  are  in  a 
state  of  equilibrium  as  regards  their  own  particular  move- 
ments. The  contraction  of  both  groups  of  one  side, 
alternately,  results  then  in  lateral  rolling.  If  we  flex  at  the 
lumbar  region  or  extend,  the  pre-vertebral  and  post-vertebral 
muscles  are  in  a  state  of  alternate  relaxation  and  contraction, 
and  lateral  movement  is  not  permissible,  as  we  can  readily 
prove  on  ourselves.  When  we  lie  down  with  the  spine  fixed 
and  the  pelvis  and  the  lower  limbs  free,  this  lateral  action, 
i.e.  the  combined  action  of  the  pre-vertebral  and  post- 
vertebral  muscles  on  one  side  raises  the  pelvis  and  lower 
limb  on  the  same  side,  and  depresses  them  on  the  other. 
This  action  causes  the  so-called  "  pelvic  tilt."  In  this 
position  the  normal  relationship  of  the  anterior  superior 
spines  to  the  medial  abdominal  plane  or  to  the  umbilicus 
is  upset,  producing  apparent  lengthening  and  apparent 
shortening  of  the  lower  limbs.  This  is  independent,  as  seen 
in  cases  of  hip  disease,  of  the  position  assumed  at  the  hip 
joint,  which  is  dependent  solely  on  the  action  of  the  muscles 
whose  fulcrum  or  centre  of  motion  is  at  that  articulation. 

Spinal  Rest 

Weakness  of  the  neck  muscles  (paralysis),  with  inability 
to  hold  the  head  erect,  is  not  frequent  in  infantile  paralysis  ; 
in  a  series  of  100  cases  it  was  only  met  with  twice — and  in 
both  instances  it  was  associated  with  paralysis  of  all  four 
limbs  and  inability  to  sit  up.     These  cases  do  well,  owing,  I 


220  THE    ACTION    OF   MUSCLES 

apprehend,  to  the  fleshy  character  of  the  cervical  muscles 
and  to  the  good  natural  rest  recumbency  affords — main- 
tenance of  which  alone,  apart  from  the  encouragement  of 
voluntary  muscular  action,  usually  suffices  for  recovery. 
"  Paralysis/'  of  the  back  muscles,  associated  with  inability 
to  maintain  the  erect  position  when  sitting  in  bed,  is  more 
frequently  met  with  than  cervical  affection,  and  usually 
accompanies,  in  poliomyelitis,  affection  of  all  four  limbs 
and  frequently  paralysis  of  the  two  lower  ones.  Complete  rest 
of  the  trunk  and  lower  limbs  in  a  double  Thomas's  splint, 
and  with  an  extension  to  the  head  to  prevent  dor  si-flexion, 
if  neck  affection  be  present,  is  advisable.  With  effective 
rest  at  the  outset  good  recovery  with  absence  of  deformity 
is  the  rule. 

In  the  absence  of  effective  rest,  pelvic  tilting  or  spinal 
curvature,  or  both,  are  serious  possibilities.  There  is 
little  doubt  that  the  majority  of  cases  of  severe  lateral 
curvature  are  the  result  of  neglected  or  inefficient  rest 
treatment  in  cases  of  infantile  paralysis.  So  important  do 
I  regard  this,  that  in  a  case  of  upper  limb  paralysis,  not 
only  should  the  upper  limb  be  rested  in  the  abduction 
frame,  but  recumbency  for  a  month  should  be  insisted  on, 
for  the  sake  of  convenience,  in  a  double  Thomas's  hip  splint. 
Only  in  this  way  can  the  danger  of  lateral  deviation  of 
the  spine  or  rotation  be  anticipated.  Not  only  is  the 
treatment  harmless,  but  from  every  point  of  view  beneficial. 
Pelvic  tilting  from  paralysis  of  the  groups  of  one  or  other 
side,  if  not  guarded  against,  occurs  rapidly,  and  even  in 
infants  may  resist  all  forcible  measures  for  its  correction. 
Its  prevention  is  simple.  It  is  associated  with  apparent 
lengthening  or  shortening  of  one  limb  or  the  other,  and 
later,  with  the  usual  production  of  lateral  curvature  of 
the  spine.  Recumbency  in  a  double  Thomas's  splint,  with 
the  lower  limbs  evenly  abducted,  will  be  sufficient  to 
obviate  this  ;  or  in  the  absence  of  cervical  or  upper  limb 
affection,  rest  in  a  lower  limb  abduction  frame,  with  equal 
abduction  of  the  lower  limbs,  will  suffice. 

In  fig.  92  is  illustrated  a  girl  aged  three  years,  the  victim 


WHICH    MOVE   THE   BACK   AND    LOINS     221 

of  poliomyelitis.  She  was  untreated  by  any  form  of  splint, 
and  the  condition  shown  was  present  eight  weeks  after  the 
onset.  There  is  marked  pelvic  tilting,  with  apparent 
lengthening  of  the  lower  limb  on  the  affected  right  side 
and   shortening  on  the  non-affected  left   side.     There  is 


Fig.  92. — Pelvic  tilting  following  poliomyelitis. 

spinal  curvature  present,  and  the  tilting  did  not  respond 
to  even  forcible  traction.  In  a  case  such  as  this  the  inclina- 
tion is  to  raise  the  boot  on  the  shortened,  though  sound,  left 
pelvic  side.  The  raising  should  be  on  the  right,  apparently 
lengthened,  limb,  so  as  to  throw  the  pelvis  as  much  as  possible 
on  to  the  left  shortened  one.  Ultimately,  in  this  neglected, 
avoidable,  and  unresponding  condition  the  boot  had  to  be 
raised  on  the  shortened  left  side  to  enable  the  patient  to 
ambulate.  The  pelvic  tilting  was  due  to  a  paresis  affecting 
the  quadratus  lumborum  and  the  erector  spinae  on  the 
right  side,  with  uncontrolled  action  of  the  same  muscles  on 
the  left  side  producing  the  tilt  and  shortening. 


CHAPTER    XIV 

ANATOMICAL    CONSIDERATIONS    IN   JOINT 
FIXATION 

The  Significance  op  Fixation  and  Cure 

The  use  of  joints  in  the  economy  is  varied,  and  associated 
mainly  with  improvement  of  active  and  passive  mobility, 
and  hence  of  the  utility  of  the  otherwise  rigid  limb  ;  also 
with  the  lessening  of  the  risk  of  fractures  and  the  dissi- 
pation of  jars.  Correlative  and  commensurate  with  the 
increased  mobility  of  a  joint,  we  find  a  multiplication 
and  specialization  of  the  muscles  which  act  at  it.  Of  the 
major  joint  functions — active  and  passive  mobility  and 
anti-concussion — active  or  muscular  mobility  is  by  far  the 
most  important.  Hence  we  can  say  that  morphologically 
and  physiologically  a  joint  is  dominated  by  the  muscles 
which  act  across  it.  For  the  muscle  the  joint  exists, 
not  the  muscle  for  the  joint.  When  we  deal  with  the 
question  of  immobilization  of  a  limb  or  part  of  a  limb  for 
the  purpose  of  conferring  "  perfect  rest  "  upon  a  damaged 
or  diseased  joint,  the  muscular  factor  should  always  be 
regarded  as  the  important  one.  An  endeavour  must  be 
made  effectively  and  accurately  to  counteract  the  active 
and  passive  forces,  which  tend  to  alter  that  disposition  of 
the  component  parts  of  the  joint  which  has  been  selected 
by  the  surgeon.  This  disposition  may  be  advised  as  being 
the  most  appropriate  for  securing  ankylosis  on  the  one 
hand,  or  for  obtaining  improved  or  normal  range  of  move- 
ment on  the  other. 

When  we  speak  of    perfect    rest   of   a   joint    we   refer 
of  course  to  that  position  in  which   passive  contact   of 

222 


ANATOMICAL    CONSIDERATIONS  223 

damaged  areas  is  reduced  to  a  minimum  by  the  proper  dis- 
position of  the  parts,  and  friction  contact  is  eliminated  by 
appropriate  fixation.  Counter-action  of  the  passive  forces 
— largely  gravitational — can  be  easily  and  effectively  accom- 
plished. But  when  we  come  to  consider  the  counteraction 
of  the  active  forces  operating  against  the  maintenance  of 
the  position  of  "  perfect  rest,"  our  attention  must  be  paid 
to  the  origins  and  insertions  of  the  muscles  which  act  at 
the  joint.  The  results  aimed  at  in  the  treatment  of  diseased 
joints  may  be  practically  divided  into  two  groups  : 

(1)  Those  in  which  recovery  takes  place  with  a  complete 
or  partial  restoration  of  the  articular  function. 

(2)  Those  in  which  subsequent  mobility  being  hopeless, 
we  endeavour  to  concentrate  our  attention  on  such  fixation 
of  the  component  elements  of  the  joint  as  will  be  most 
utilitarian  when  ankylosis  occurs. 

As  regards  the  first  group,  the  affected  joint  is  recovering 
when  the  range  of  motion  of  its  component  elements  tends 
not  to  be  diminished,  but  increased  towards  the  normal. 
The  progress  of  the  cure  is  from  the  zero  position  of 
rest,  along  the  lines  of  normal  directions  of  motion,  up  to 
the  limiting  points  of  normal  degree  of  motion  along  those 
lines ;  the  attainment  of  this  represents  the  perfection  of 
cure. 

When  our  ideal  is  adequate  fixation,  no  subsequent 
alteration  of  the  relation  of  the  components  forming  a 
utilitarian  ankylosis  should  eventuate.  Regarded  from  the 
evolutionary  standpoint,  there  is  a  much  higher  specializa- 
tion and  correlation  with  intellectuality  in  the  upper 
than  in  the  lower  limb.  It  is  more  important  to  prevent 
ankylosis  in  the  upper  than  in  the  lower  extremity.  The 
main  function  of  the  lower  limb  is  the  support  of  the  body 
in  the  erect  position  ;  and  in  spite  of  ankylosis  of  the 
three  major  joints  a  patient  may  still  be  able  to  walk. 
In  man,  so  even  is  the  muscular  adjustment  in  the  upper 
limb  that  the  loss  of  function  of  the  adductor  and 
opponens  pollicis  or  of  the  pronator  teres  may  be 
sufficient    to    ruin    its    usefulness.      In    the    lower    limb, 


224 


THE   ACTION    OF    MUSCLES 


since  it  is  necessary  to  protect  the  joints  from  the  shocks 
of  locomotion  and  weight-bearing,  recumbency  should 
be  insisted  upon  at  all  times  in  diseased  or  damaged 
conditions.  As  illustrations  of  these  principles  we  may 
take  the  cases  of  the  ankle  and  knee  in  the  lower,  and  the 
wrist  and  elbow  joints  in  the  upper  extremities. 

Ankle  Joint. — Here  the  position  for  rest  and  recovery,  or 
for  ankylosis,  should  be  with  the  foot  at  a  right  angle — 
over- action  of  the  extensors,  peronei,  or  tibials  being  associ- 
ated with  deformity,  since  it  produces  equinus,  valgus,  or 
varus.  Owing  to  the  position  of  origin  of  the  ankle  ex- 
tenders forming  the  tendo  achillis  there  can  be  no  rest 
of  ankle  unless  the  power  of  action  of  these  muscles  is 
prevented.  So-called  immobility  is  usually  secured  by 
means  of  plaster  of  Paris  applied  round  the  joint,  or  by 
means  of  a  splint  passing  to  the  upper  third  of  the  leg. 
These  measures  not  only  do  not  rest  the  knee  joint,  but 
are  often  ineffectual  to  prevent  inversion  or  eversion  of  the 
foot  or  flexion  of  the  toes. 

These  difficulties  are  overcome  by  means  of  the  extended 


-T  THIGH    WING. 


KNEE  JOINT. 


Fig.  93. — The  extended  arc  splint. 


arc  splint  (fig.  93)  which  passes  above  to  the  junction  of 
the  upper  and  middle  thirds  of  the  thigh,  the  construc- 
tion of  which  has  already  been  described  (chap,  v,  p.  198). 
Should  the  ankle  require  dressing,  such  alteration  may  be 
made  in  the  leg-piece  as  will  permit  of  this  without  inter- 


ANATOMICAL    CONSIDERATIONS 


225 


fering  with  the  immobility  of  the  joint.     The  position  of 
the  straps  may  be  altered  to  suit  any  individual  case. 

Knee  Joint.— The  ideal  position  for  rest  or  ankylosis  is 
almost  complete  extension.  Adequate  rest  can  only  be 
secured  by  such  a  position  as  secures  immobility  of  both 


C        CHEST  WING. 


f  THIGH  WING. 


KNEE  JOINT. 


Fig.  94. — Effective  splint  for  resting  the  knee  joint. 


the  ankle  and  hip,  owing  to  the  positions  of  origin  and 
insertion  of  the  muscles  about  the  knee.  This  may  be 
obtained  by  means  of  a  single  Thomas's  splint  to  which  the 
ankle  arc  shoe  is  attached  (fig.  94).  If  sinuses  be  present 
the  wings  may  be  altered  to  admit  of  dressing  without 
interfering  with  the  immobility  of  the  limb.  Under  this 
15 


226  THE    ACTION    OF    MUSCLES 

treatment  no  contracture  can  occur,  and  the  condition  can 
be  under  daily  observation. 

The  Thomas  caliper  splint,  with  the  stems  made  of  hollow 
tubular  steel,  is  the  ideal  splint  for  use  when  the  patient 
commences  to  ambulate.  Plaster  of  Paris,  extending  from 
the  mid  thigh  to  the  mid  leg,  is  for  many  reasons  absolutely 
worthless,  and  is  the  cause  of  so-called  "  rest  treatment " 
being  frequently  followed  by  amputation. 

Wrist  Joint. — At  this  joint  rest  is  usually  secured  by 
means  of  a  flat  wooden  splint,  or  by  means  of  a  "  cock-up  " 
splint,  which  may  be  of  metal,  as  in  the  Thomas  hand  splint 
which  produces  extension  of  the  wrist  and  fingers,  or  of 
wood,  as  in  Lister's  splint  in  which  the  wrist  is  extended 
and  fingers  flexed  over  a  cork  piece — the  limb  being  either 
supported  in  a  sling  or  left  dependent.  Since,  however, 
none  of  these  control  the  elbow,  and  since  flexors  and 
extensors  of  the  fingers  and  wrist  arise  above  the  elbow 
joint  from  the  humerus,  they  cannot  be  regarded  as  perfect 
splints  for  securing  strictly  anatomical  rest  of  the  joint. 
For  ankylosis,  fixation  in  the  extended  position,  owing  to 
the  improved  leverage  thus  given  to  the  flexors,  admits  of 
a  strong  grip  ;  fixation  in  the  flexed  position  of  a  weak 
grip.  Furthermore,  a  wrist  fixed  in  the  position  of  over- 
pronation  is  worthless,  since  flexion  of  the  elbow  would 
bring  the  back  of  the  hand  to  the  mouth.  Similarly 
with  fixation  in  the  over-supinated  position,  in  which  food 
may  be  brought  to  the  mouth  on  flexing  the  elbow,  but  the 
power  of  grasping  the  food  is  lost. 

Elbow  Joint. — Here  the  usual  treatment  is  a  rectangular 
splint  or  plaster  of  Paris — with  the  risk  of  ankylosis  in  a 
useless  position,  to  say  nothing  of  the  interference  with 
mobility  if  sinuses  be  present — or  the  position  of  acute 
flexion  by  means  of  a  cervical  slinger,  the  range  of  flexion 
being  increased  with  recovery.  By  these  methods  neither 
the  shoulder  joint,  through  which  the  long  head  "of  the 
biceps  courses,  nor  the  wrist  joint  is  rested,  nor  in  the  case 
of  the  latter  appliance  is  the  joint  itself  protected  from  local 
irritation.    The  ideal  fixation  would  be  rest  in  a  position  of 


ANATOMICAL   CONSIDERATIONS  227 

flexion  at  about  45 °,  securing  rest  also  for  the  shoulder  and 
wrist — the  angle  of  flexion  as  enunciated  by  Thomas  being 
increased  with  recovery.  If  ankylosis  be  intended,  this 
should  be  obtained  in  a  position  of  flexion  most  suitable 
for  the  patient's  trade  or  occupation. 

In  the  upper  extremity,  so  fine  and  correlated  are  the 
muscular  adjustments  that  adequate  fixation  of  one  joint 
is  best  secured  by  fixation  of  all  three,  a  point  which  never 
seems  to  be  insisted  upon.  This  may  be  simply  obtained 
by  means  of  the  writer's  upper  limb  abduction  splint  (fig.  18). 
By  its  means  the  shoulder  is  supported,  and  the  elbow  joint 
may  be  placed  in  any  angle  of  flexion  necessary.  This 
can  be  altered  with  recovery  or  remain  fixed  at  any  angle 
for  adequate  ankylosis  should  this  be  the  result  desired. 
By  means  of  the  hand-piece  the  wrist  and  fingers  may  be 
extended  and  the  hand  placed  midway  between  pronation 
and  supination.  In  spite  of  the  presence  of  sinuses  which 
require  dressing,  the  limb  is  always  at  rest  whilst  this  is 
being  done,  and  furthermore,  the  position  of  the  wings  may 
be  altered  for  the  individual  case  without  interfering  with  its 
effectiveness.  In  altering  the  angle  of  flexion  at  the  elbow 
joint  with  the  limb  supported  by  the  abduction  splint,  we 
have  this  advantage  over  the  position  of  acute  flexion 
produced  by  a  sling,  that  we  are  working  with  muscles  whose 
origin  and  insertion  are  as  nearly  as  possible  on  a  level  plane. 
It  is  worth  remembering  that  in  separation  of  the  epiphysis 
of  the  humerus,  where  the  treatment  usually  adopted  is 
acute  elbow  flexion  by  means  of  adhesive  strapping,  the 
same  position  can  be  obtained  by  means  of  the  abduc- 
tion splint.  This  has  the  advantage,  that  the  elbow,  often 
greatly  swollen,  is  supported,  and  alterations  in  the  angle 
of  the  joint  can  be  effected  by  means  of  a  hinge  in  the  splint 
without  disturbing  the  fracture.  Furthermore,  the  limb 
is  not  compressed,  thus  avoiding  the  liability  to  ischaemic 
"paralysis"  of  the  forearm,  of  which  unfortunately  the 
strapping  is  a  not  infrequent  cause. 


CHAPTER    XV 
THE    MUSCLES    OF    RESPIRATION 

These  we  may  consider  under  three  divisions,  viz.  : 

(i)  Muscles  of  the  abdominal  wall. 

(2)  Muscles  of  the  diaphragm. 

(3)  Muscles  of  the  thorax. 

I.    Muscles  of  the  Abdominal  Wall 

These  are  five  in  number  on  each  side,  although  the  fifth 
pair  is  almost  extinct  in  man.  They  are  external  oblique, 
internal  oblique,  transversalis,pyramidalis,  rectus  abdominis, 
and  extend  between  the  thorax  and  the  pelvis. 

.  External  Oblique  (Descendens). — This  is  the  outermost 
and  largest  of  the  abdominal  muscles,  being  muscular  later- 
ally and  tendinous  in  front.  Above,  it  is  attached  to  the 
lower  eight  ribs  by  eight  fleshy  processes  or  digitations,  and 
the  muscular  fibres  pass  obliquely  downwards  and  forward. 
Dorsally,  the  muscle  fibres  from  the  lower  ribs  are  attached 
to  the  anterior  half  of  the  crest  of  the  ilium.  The  rest  of  the 
fleshy  muscle,  the  middle  and  upper  portions,  terminates 
in  an  aponeurosis  which,  covering  the  whole  of  the  front 
of  the  abdomen,  joins  with  that  of  the  opposite  side  at  the 
mid  line,  the  union  being  known  as  the  linea  alba  ;  this 
extends  from  the  sternum  to  the  pubes.  Below,  the 
aponeurosis  extends  from  the  anterior  superior  spine  of 
the  ilium  to  the  crest  of  the  os  pubis.  This  lower  limit  is 
the  inguinal  or  Poupart's  ligament.  In  the  lower  part  of  the 
aponeurosis,  close  to  the  spine  of  the  pubis,  lies  the  external 
abdominal  or  subcutaneous  inguinal  "  ring/'  Formerly, 
many    anatomists   regarded    the    inguinal    ligament    as    a 

228 


THE   MUSCLES    OF    RESPIRATION  229 

distinct  band  into  which  the  aponeurosis  of  the  external 
oblique  was  inserted,  and  not  as  part  of  the  aponeurosis 
itself.  In  general,  however,  in  the  mammalia  below  man, 
the  external  oblique  has  no  attachment  to  the  iliac  crest, 
and  the  aponeurosis  from  the  lower  dorsal  muscle  fibres 
passes  directly  across  the  internal  oblique  to  the  external 
ring.  Comparing  this  arrangement  with  Poupart's  liga- 
ment in  man,  Arthur  Keith  regards  it  as  one  serving  to 
strengthen  the  inguinal  region,  and  so  lessening  the  liability 
to  hernia. 

Internal  Oblique  (Ascendens).— This  lies  between  the 
external  oblique  and  transversalis,  and  is  attached  below 
to  the  outer  half  of  the  inguinal  or  Poupart's  ligament, 
anterior  two  thirds  of  the  crest  of  the  ilium,  and  dorsally 
to  the  lumbar  fascia.  From  this  origin  the  fibres  spread 
in  a  somewhat  fan-shaped  form.  Behind  they  pass  directly 
to  the  lower  three  ribs.  In  front  they  form  an  aponeurosis, 
which,  at  the  linea  semi-lunaris,  splits  to  form  with  the 
aponeurosis  of  the  external  oblique  and  transversalis  muscles 
the  sheath  of  the  rectus  ;  and  is  finally  inserted  into  the 
seventh,  eighth,  and  ninth  costal  cartilages  above  and  into 
the  linea  alba  from  the  ensiform  cartilage  to  the  symphysis 
pubis.  The  fibres  from  Poupart's  ligament  pass  downwards 
and  inwards  across  the  spermatic  cord,  and  are  inserted, 
by  means  of  a  tendon,  with  fibres  of  the  transversalis  into 
the  pubic  crest  and  ilio-pectineal  line,  forming  the  con- 
joined tendon. 

Transversalis. — This  is  the  inner  of  the  flat  muscles  of  the 
abdomen,  and  is  so  called  on  account  of  the  direction  of  the 
fibres.  Its  origin  below  is  from  the  outer  third  of  Poupart's 
ligament,  anterior  two  thirds  of  the  iliac  crest,  behind  from 
the  lumbar  fascia,  and  above  from  the  inner  surfaces  of  the 
cartilages  of  the  lower  six  ribs.  The  fibres  pass  horizontally 
forwards,  to  terminate  in  an  aponeurosis  which  is  inserted 
into  the  linea  alba,  the  upper  three  fourths  passing  behind  the 
rectus  and  the  lower  fourth  as  in  the  case  of  the  aponeurosis  of 
the  external  and  internal  oblique,  passing  in  front  of  the 
sheath  of  the  rectus      Some  of  the  fibres  of  the   aponeurosis 


230  THE   ACTION   OF   MUSCLES 

below  arch  downwards,  and  are  inserted  with  fibres  of  the 
internal  oblique  into  the  os  pubis,  forming  the  conjoined 
tendon. 

Pyramidalis. — This  small  muscle  may  be  wanting  on  one 
or  both  sides.  It  arises  below  from  the  pubic  crest,  and 
passing  up  and  in  terminates  in  the  mid  line  at  the  linea 
alba,  sometimes  extending  as  far  as  midway  between  the 
pubes  and  umbilicus.  This  muscle  has  its  greatest  develop- 
ment in  the  mono tr ernes  and  marsupials — animals  "  low  " 
in  the  mammalian  scale — and  this  is  associated  in  both 
the  male  and  female  members  of  the  two  orders  with  the 
presence  of  the  so-called  epi-pubic  or  marsupial  bone.  These 
are  two  in  number,  one  on  each  side,  and  extend  for  a 
varying  distance  up  and  out  in  the  lower  part  of  the  anterior 
abdominal  wall,  articulating  below  with  the  horizontal  ramus 
of  the  pubes.  They  are  relatively  larger  in  the  mono  tr  ernes 
than  in  the  marsupials.  In  the  former,  descent  of  the  testes 
has  not  taken  place  ;  but  although  in  the  marsupials  the 
testes  are  still  abdominal  at  the  time  of  birth,  yet  they 
descend  into  the  scrotum  shortly  after  the  young  is  trans- 
ferred to  the  pouch,  and  occupy  a  prepenial  and  not  a  post- 
penial  position.  In  the  platypus  the  three  abdominal 
muscles  are  to  be  distinguished,  and  the  pyramidalis,  or 
superior  rectus,  has  an  attachment  on  the  inner  side  of  the 
marsupial  bone,  and  meeting  its  fellow  at  the  linea  alba  may 
be  traced  as  high  as  the  sternum.  The  rectus  abdominis,  or 
deep  rectus,  is  also  attached  to  the  marsupial  bone  and 
reaches  as  high  as  the  first  rib  and  coracoid  bone.  In  the 
marsupial  the  lower  fibres  of  the  pyramidalis  are  transverse, 
below  passing  across  the  interval  between  the  two  marsupial 
bones,  while  above  they  are  oblique  in  direction.  The  rectus, 
as  in  monotremes,  may  reach  as  high  as  the  first  rib.  The 
marsupial  or  epi-pubic  bone  is  represented  in  man  by  the 
internal  pillar  of  the  external  abdominal  ring,  and  according 
to  Sir  J.  Bland-Sutton,  "  Gimbernat's  ligament  and  the 
triangular  fascia  are  remnants  of  the  very  stout  ligament 
which,  in  marsupials,  anchors  the  epi-pubic  bone  firmly 
to  the  ilio-pectineal  line." 


Fig.  95. — Dissection  of  ventral  surface  of  the  platypus  (abdomen  and  thigh). 
f,   Pectoralis  major,     r,  Rectus  abdominis,     e,   IJxt.  oblique,     p,   Pyramidalis  (sup. 
rectus),     m,  Sartorius.     b,  Adductors,     a,  Gracilis,     v,  Tibialis  anticus.     c,  IYeg  flexors. 
k,    Cowper's  glands,     s,   Fibres  from  gracilis  to  sphincter,     t,   Adductor  intertibialis. 
w,  Tail. 

230] 


THE   MUSCLES    OF    RESPIRATION  231 

Rectus. — This  muscle  extends  along  the  front  of  the 
abdomen  from  the  sternum  to  the  pubes.  In  the  mid  line 
between  the  two  muscles  lies  the  linea  alba,  which  is  the 
meeting  place  of  the  aponeuroses  of  the  oblique  and  trans- 
versalis  muscles,  and  can  be  regarded  as  the  fibrous  con- 
tinuation of  the  sternum  to  the  pubes. 

Below,  each  muscle  is  attached  by  two  heads  to  the  sym- 
physis and  crest  of  the  os  pubis.  Above,  it  is  inserted  into 
the  lower  end  of  the  sternum  and  fifth,  sixth,  and  seventh 
costal  cartilages.  The  sheath  of  the  rectus  consists  in 
front  of  the  aponeurosis  of  the  external  oblique  and  half 
the  thickness  of  the  internal  oblique,  and  behind  of  the 
aponeurosis  of  the  transversalis  and  the  dorsal  half  of  the 
internal  oblique.     This  is  only  in  the  upper  three  fourths. 

The  lower  fourth  of  the  rectus  has  no  dorsal  sheath,  since 
the  aponeuroses  of  the  abdominal  muscles  pass  in  front. 
Crossing  the  rectus  are  three  to  five  tendinous  transverse 
intersections — linese  transversa^.  These  are  not  often  found 
below  the  umbilicus,  and  are  to  be  regarded  as  analogous  to 
ribs  which  are  developed  in  man  in  connection  with  the 
thoracic  and  not  the  abdominal  muscles.  Amongst  reptilia, 
for  example  the  crocodile,  bony  abdominal  ribs  are  found. 
The  lineae  semi-lunares  are  two  curved  tendinous  lines,  one 
on  each  side,  corresponding  to  the  outer  edges  of  the  rectus 
muscle.  They  are  formed  by  the  junction  of  the  aponeu- 
roses of  the  lateral  muscles. 

II.  Muscles  of  the  Diaphragm 

Diaphragm. — This  is  a  vaulted  musculo-fibrous  partition 
separating  the  cavity  of  the  thorax  from  that  of  the 
abdomen.  Its  upper  or  thoracic  surface  is  convex,  and 
its  lower  or  abdominal  is  concave.  Its  longest  diameter 
is  lateral  and  not  dorso- ventral,  the  periphery  of  the  dia- 
phragm is  muscular  and  the  centre  tendinous,  being  ex- 
panded or  aponeurotic.  Its  periphery  is  attached  to  the 
whole  of  the  inner  circumference  of  the  thorax,  being  attached 
in  front  to  the  ensiform  cartilage  of  the  sternum,  laterally 


232  THE   ACTION    OF    MUSCLES 

to  the  inner  surface  of  the  lower  six  ribs  interdigitating  with 
the  transversalis.  On  account  of  this  Bartholin  regarded 
the  diaphragm  and  the  transversalis  as  but  a  single  three- 
bellied  muscle,  an  opinion  not  far  from  the  truth,  since 
morphologically  the  triangularis  sterni,  transversalis 
abdominis,  diaphragm,  and  levator  ani  are  portions  of  one 
compressor  sheet  with  the  power  of  acting  functionally 
together.  Dorsally  it  is  attached  to  the  lumbar  vertebrae 
by  means  of  the  two  crura  and  the  inner  and  outer  arcuate 
ligaments.  The  crura  are  two  muscular  bundles,  one  on 
each  side,  attached  to  the  upper  lumbar  vertebrae,  and  de- 
cussate before  reaching  the  central  tendon.  The  inner  arcu- 
ate ligament  on  each  side  arches  over  the  psoas,  between  the 
body  and  transverse  process  of  the  first  lumbar  vertebrae. 
The  outer  arcuate  ligament  arches  on  each  side  over  the 
upper  end  of  the  quadratus  lumborum,  and  passes  from 
the  transverse  process  of  the  first  lumbar  vertebra  to  the 
last  rib.  From  the  periphery  the  muscular  fibres  converge 
to  a  tri-lobed  central  tendon  which  lies  nearer  the  ventral 
than  the  dorsal  surface.  The  diaphragm  is  proportionately 
longest  and  most  fleshy  in  the  cetacea  than  in  any  other 
mammalian  class,  there  being  only  a  slight  central  tendon. 
The  object  of  this  is  to  allow  the  necessary  distension  of  the 
lungs,  which,  as  in  the  dugong,  act  as  air  bladders.  Amongst 
certain  of  the  ungulates  also,  in  which  we  have  movable 
ribs  continued  to  near  the  pelvis,  the  diaphragm  is  propor- 
tionately large. 


III.    Muscles  of  the  Thorax 

The  true  muscles  of  the  ribs  are  : 

External  intercostals. 

Internal  intercostals. 

Serratus  posticus  superior. 

Serratus  posticus  inferior. 

Levatores  costarum. 

Triangularis  sterni. 
External  Intercostals. — These  are  eleven  on  each  side, 


THE    MUSCLES    OF    RESPIRATION  233 

occupying  with  the  internal  intercostals  the  spaces  between 
the  ribs.  They  pass  obliquely  downwards  and  forwards 
in  a  direction  similar  to  the  fibres  of  the  external  oblique 
of  the  abdomen,  from  the  lower  border  of  one  rib  to  the 
upper  border  of  the  rib  below. 

Internal  Intercostals. — These  are  eleven  on  each  side, 
and  their  fibres  are  directed  obliquely  downwards  and  back- 
wards like  the  internal  oblique  of  the  abdomen.  They  pass 
from  the  inner  surface  of  each  rib  and  the  corresponding 
costal  cartilage,  and  are  inserted  into  the  upper  margin  of 
the  rib  below.  Passing  in  the  same  direction,  but  on  a 
deeper  level,  are  the  Infracostales.  These  irregular  bundles 
lie  on  the  inner  surface  of  the  ribs.  They  may  pass  between 
three  or  more  ribs  near  the  angles,  and  are  found  especially 
in  connection  with  the  lower  ribs. 

Serratus  Posticus  Superior. — This  lies  flat  at  the  upper 
and  back  part  of  the  chest,  and  arises  on  each  side  from  the 
spines  of  the  last  cervical  and  upper  three  thoracic  vertebrae, 
and,  passing  down  and  outwards,  is  inserted  into  the  second, 
third,  fourth,  and  fifth  ribs. 

Serratus  Posticus  Inferior.— This  is  placed  at  the  lower 
part  of  the  back,  and  arises  on  each  side  from  the  spines 
of  the  last  two  thoracic  and  upper  two  lumbar  vertebras. 
Its  fibres  pass  up  and  out,  and  are  inserted  into  the  four 
lower  ribs. 

Levatores  Costarum  or  Supracostales. — These  small 
muscular  bundles,  twelve  on  each  side,  might  almost  be  re- 
garded as_  portion  of  the  external  intercostals,  just  as  the 
infracostales  are  of  the  internal  intercostal.  They  lie  close 
to  the  spine,  and  arise  from  the  transverse  processes  of  the 
last  cervical  and  upper  eleven  thoracic  vertebrae,  and 
passing  downward  and  outward  are  inserted  each  into  the 
outer  surface  of  the  rib  below  them,  close  to  the  angle. 

Triangularis  Sterni. — This  lies  on  the  inner  surface  of 
the  front  of  the  chest.  It  arises  from  the  side  of  the  meso- 
sternum  or  manubrium  and  the  inner  surface  of  the  lower 
sternum  or  ensiform,  and  its  fibres  pass  up  and  out,  to  be 
inserted  into  the  cartilages  of  all  the  ribs  from  the  second 


234  The  action  of  muscles 

to  the  sixth.     The  lower  fibres  are  continuous  with  those 
of  the  transversalis  abdominis. 


Action  of  Abdominal  and  Thoracic  Muscles 

All  these  muscles,  including  the  diaphragm,  are  essentially 
muscles  of  respiration.  The  principal  muscle  of  inspiration 
— indeed  of  respiration  generally — is  the  diaphragm,  which 
was  well-named  "  Nobilissimus  post  cor  musculus."  When 
it  acts  the  thorax  enlarges  and  air  enters  the  lungs.  The 
enlargement  of  the  lungs  is  pari  passu  with  the  enlargement 
of  the  thorax,  and  any  possibility  that  a  vacuum  would  be 
formed  is  thereby  obviated.  Pressure  is  transmitted  to  the 
abdominal  viscera,  and  in  turn  to  the  abdominal  muscles, 
which  being  the  antagonists  of  the  diaphragm,  are  during 
its  action  relaxed  and  elongated.  Distension  of  the  air 
vesicles  and  the  interchange  of  gases  then  constitutes  the 
stimulus  to  action  of  the  relaxed  and  stretched  abdominal 
muscles.  These  contract,  and  not  only  pull  down  and 
compress  the  thorax,  but  react  also  on  the  abdominal  viscera, 
with  the  result  that  the  now  relaxed  diaphragm  becomes 
in  its  turn  elongated  and  restored  to  its  normal  state  of 
upward  convexity  ;  and  the  thorax  becomes  diminished  in 
diameter,  as  well  as  in  the  air-carrying  capacity  of  the 
lungs.  Such  in  brief  is  in  my  opinion  the  essence  of  the 
respiratory  movements.  These  are  carried  out,  not  by 
the  lungs,  but  by  the  muscles  of  the  thorax  and  abdomen. 
In  the  case  of  the  respiratory  mechanism  we  have  for 
consideration  the  action  of  muscles  that  are*  not  only 
involuntary,  but  are  also  capable  of  being  controlled  by 
the  will.  Oxygen  is  as  essential  for  the  body  when  asleep 
as  when  awake.  Voluntary  action,  on  the  other  hand,  is 
essential  for  the  production  of  the  voice,  which  depends 
on  expiration  ;  and  it  is  also  necessary  in  connection  with 
the  actions  of  the  body  as,  for  example,  in  violent  exertions. 
It  must  be  remembered  that  the  greater  the  rigidity  of 
the  trunk  the  more  effective  will  limb  action  become,  and 
especially  that  of  the  upper  extremity.     When  we  propose 


THE   MUSCLES   OF   RESPIRATION  235 

a  violent  effort  with  this  extremity  we  take  advantage  of 
a  preliminary  full  sustained  inspiration,  dependent  on  the 
maximum  effort  of  the  muscles  of  inspiration,  and  in  this 
way  improve  the  resistance  of  the  trunk. 


Function  of  the  Diaphragm 

For  the  proper  appreciation  of  the  function  of  the 
diaphragm  a  reference  must  be  made  to  its  comparative 
anatomy.  For  an  accurate  knowledge  of  this  we  are 
indebted  to  Professor  Arthur  Keith,  whose  researches  on 
this  subject  have  placed  the  principles  of  the  muscular 
mechanism  of  respiration  on  a  sound  anatomical  basis. 
The  great  characteristic  of  the  myology  of  the  mammalia 
is  seen  in  the  development  of  a  complete  diaphragm  sepa- 
rating thorax  from  abdomen.  This  is  not  more  complete 
in  man  at  one  end  of  the  scale  than  in  the  platypus  at 
the  other.  With  its  presence  there  is  associated  a  large 
increase  in  inspiratory  power.  It  is  customary  to  regard  the 
diaphragm  as  having  arisen  gradually  as  a  partition  in  the 
body  cavity,  shutting  off  the  pulmonary  from  the  abdominal 
viscera.  There  would  seem  to  be  little  doubt  however 
that  in  early  vertebrate  life  the  abdominal  muscles,  as  well 
as  the  diaphragm,  were  at  first  concerned  only  with  the 
circulation.  With  the  introduction  of  ribs  and  lungs  the  ab- 
dominal wall,  as  well  as  the  diaphragm,  became  respiratory. 
In  fish  and  amphibians  the  septum  transversum  divides 
the  body  cavity  into  two  portions — cardiac  and  abdominal ; 
and  in  the  latter  in  amphibians  the  lungs  are  situated.  In 
reptiles  the  lungs  are  still  abdominal.  In  birds  the  greater 
part  of  the  lungs  has  become  extruded  from  the  abdominal 
cavity.  From  a  study  of  the  tailed  amphibia  the  conclusion 
is  reached  that  the  mammalian  diaphragm  represents  the 
cervical  wall  or  diaphragm  of  the  amphibian  abdominal 
cavity,  which  became  perforated  by  the  development  of 
the  lungs.  As  Professor  Keith  puts  it,  "  The  lungs,  like  the 
testicles,  may  be  regarded  as  organs  extruded  as  herniae 
from  the  abdominal  cavity,  because  of  certain  physiological 


436  THE   ACTION    OF    MUSCLES 

conditions  that  became  of  functional  importance  in   the 
course  of  evolution." 

The  spinal  part  of  the  muscular  diaphragm  passes  almost 
straight  up  to  the  central  tendon,  while  the  thoracic  or 
sterno-costal  portion  passes  up  and  backwards  to  this 
insertion  also,  and  the  diaphragm  at  rest  is  domed,  the 
convexity  being  towards  the  thorax.  With  muscular  con- 
traction the  central  tendon  descends,  and  by  this  means 
the  capacity  of  the  thorax  is  increased.  It  was  formerly 
held  that  the  central  leaflet  descended  least  of  all  on  account 
of  its  attachment  to  the  pericardium,  and  the  right  leaflet 
less  than  the  left  on  account  of  the  liver.  Hilton  regarded 
the  fibrous  pericardium  as  the  fascial  insertion  of  the  mus- 
cular diaphragm.  The  central  tendon  is  intimately  bound 
to  the  pericardium,  and  in  all  mammals  the  pericardium  is 
strongly  bound  to  the  root  of  the  lungs  ;  it  follows  therefore 
that  on  inspiration  the  central  tendon,  pericardium,  heart, 
and  root  of  the  lungs,  formerly  regarded  as  stationary,  move 
downwards  and  forwards.  It  would  appear  however,  from 
X-ray  studies,  that  the  alteration  of  the  diaphragm  from 
the  arched  position  to  the  horizontal  is  not  so  marked  as 
was  formerly  supposed.  The  movement  of  the  root  is,  ac- 
cording to  Professor  Keith,  necessary  for  a  proper  expansion 
of  the  apical  and  dorsal  part  of  the  lung.  The  diaphragm 
is  not  a  muscle  acting  on  the  lungs,  but  a  muscle  which 
increases  the  capacity  of  the  chest  by  compressing  the 
abdominal  organs  like  a  piston.  This  is  rendered  possible  by 
the  reciprocal  relaxation  and  elongation  of  the  abdominal 
muscles.  While  the  relation  of  the  diaphragm  to  the  lungs 
varies,  its  relation  to  the  liver  and  the  abdominal  contents 
is  constant  throughout  the  mammalia.  In  the  monotremes 
and  marsupials,  especially  the  latter,  there  is  a  marked 
attachment  between  the  liver  and  the  diaphragm,  and  this  is 
especially  noticeable  in  the  koala.  To  allow  of  the  respiratory 
movements  of  the  abdominal  viscera,  such  as  stomach,  liver, 
kidneys,  and  spleen,  we  find  that  these  organs  are  loosely 
fixed,  moving  downwards  and  forwards  in  response  to 
diaphragmatic   contraction.       They   are  replaced   by   the 


THE    MUSCLES    OF    RESPIRATION  237 

contraction  of  the  abdominal  muscles  during  expiration, 
permitted  owing  to  the  reciprocal  relaxation  and  elongation 
of  the  antagonistic  diaphragm. 

There  is  still  much  work  to  be  done  on  the  comparative 
anatomy  of  the  diaphragm.  Even  John  Hunter  regarded 
fowls  as  possessing  a  thin  transparent  diaphragm  running 
across  the  abdomen.  In  spite  of  the  fact  that  there  is  a 
bilateral  nerve  supply,  and  that  respiration  is  voluntary  as 
well  as  involuntary,  there  is  yet  wanting  any  direct  evidence 
that  the  right  and  left  sides  of  the  diaphragm  have  in- 
dependent action.  Embryology  and  experiments  on  the 
central  nervous  system  tend  to  disprove  the  view  of  bilateral 
independence.  A  relative  inequality  in  action  between  the 
right  and  left  sides  can  be  regarded  as  having  a  pathological 
and  not  a  logical  basis. 


Function  of  the  Abdominal  Muscles 

The  abdominal  muscles,  which  are  essentially  respiratory 
—being  the  direct  antagonists  of  the  diaphragm — should 
be  regarded  as  continuous  with  the  thoracic  muscles 
(although  ribs  have  developed  in  connection  with  the  latter), 
of  which  morphologically  they  are  a  part.  In  reptiles, 
birds,  and  mammals  we  have  the  specialization  of  ribs 
and  intercostal  muscles  for  purposes  of  respiration.  In 
fish  the  primitive  arrangement  of  the  muscles  of  the  body 
wall  which  forms  the  basis  of  that  seen  in  man,  is  a  ventral 
longitudinal  system  and  a  lateral  or  oblique  system.  In 
the  long-tailed  amphibian  three  muscular  layers  are  present 
in  the  body  wall,  of  which  the  middle  or  internal  oblique 
is  the  most  important,  as  the  transversalis  and  external 
oblique  layers  are  derived  from  it  during  development. 
Within  the  middle  or  internal  oblique  layer  the  ribs  are 
evolved.  The  intercostal  muscles  and  the  internal  oblique 
of  the  abdomen  are  its  representatives  in  man.  Since  in 
the  amphibians  the  lungs  are  filled  through  the  pharynx 
by  the  action  of  the  muscles  under  the  jaw,  ribs  and  in- 
tercostal muscles  as  well  as  the  diaphragm  are  primarily 


238  THE    ACTION    OF    MUSCLES       . 

evolved,  not  in  connection  with  respiration,  but  with  circu- 
lation. They  assist  in  regulating  abdominal  tension,  and 
so  the  venous  circulation.  In  a  similar  way  abdominal 
ribs  act,  as  is  seen,  for  example,  in  the  crocodile.  In  a 
transverse  section  of  the  thoracic  wall  of  a  reptile  we 
find  three  layers :  outer  represented  by  the  rectus  and 
external  oblique,  inner  by  the  transversalis,  and  a  middle 
double  layer  represented  by  the  internal  and  external 
intercostals  which  in  the  abdomen  are  combined  as  one 
layer,  the  internal  oblique.  From  the  primitive  trans- 
versalis sheet  is  formed  the  diaphragm,  triangularis  sterni, 
transversalis  abdominis,  and  the  levator  ani.  With  the 
evolution  of  lungs,  and  assisted  by  ribs  which  enabled 
the  muscles  not  only  to  compress  the  body  cavity  but  to 
allow  of  its  expansion,  the  body  musculature,  though 
primarily  circulatory  in  function,  became  respiratory. 
Further,  with  the  evolution  of  the  diaphragm  as  seen  in 
mammals,  and  the  extrusion  of  the  lungs  from  the  abdomen, 
the  musculature  of  the  body  wall  controlled  not  only  ab- 
dominal but  also  thoracic  pressure  as  well. 

With  the  erect  or  orthograde  posture  of  the  anthropoid 
and  man  there  was  a  further  functional  modification  in 
the  use  of  the  abdominal  muscles.  The  shape  of  the  chest 
altered,  the  azygos  lobe  of  the  right  lung  between  the  heart 
and  diaphragm,  which  is  well  developed  in  monotremes  and 
marsupials,  disappeared,  and  the  heart  came  to  rest  on  the 
diaphragm  ;  so  that  the  abdominal  muscles  not  only  became 
respiratory,  but  had  to  support  the  abdominal  organs  as 
well.  The  abdominal  muscles  are  the  physiological  anta- 
gonists of  the  diaphragm,  not  of  the  extensor  muscles 
of  the  spine,  hence  they  do  not  produce  by  their  action 
flexion  or  rotation  of  the  trunk.  Contraction  of  the  rectus 
does  not  call  into  physiological  relaxation  the  erector 
spinse,  which  has  not  the  same  centre  of  motion.  In 
reference  to  the  erroneous  idea  that  the  rectus  abdominis 
is  an  important  bender  of  the  trunk  when  we  stoop  from 
the  erect  position  to  pick  up  an  object  from  the  ground, 
it  is  worth  remembering  that  in  the  platypus — an  aquatic 


•THE   MUSCLES    OF    RESPIRATION  239 

mammal — the  rectus  is  relatively  better  developed  than 
in  man  and  that  a  pyramidalis  also  is  present,  as  well  as 
an  epi-pubic  bone. 

No  doubt  the  peculiar  arrangement  of  the  abdominal 
muscles  is  for  purposes  of  increased  strength  in  relation 
to  visceral  support.  The  arrangement  is  such  as  to  form, 
not  a  plane,  but  a  curved  surface,  and  of  such  a  mechani- 
cal nature  that,  whilst  the  perpendicular  pressure  is  a 
constant,  the  tangential  pressure  is  a  variable  quantity. 
One  could  not  imagine  a  better  mechanical  arrangement  for 
the  prevention  of  ventral  hernia  than  that  by  which  flat 
muscles,  whose  fibres  run  in  different  directions,  are  placed 
one  on  top  of  another.  Elastic  tissue  alone  instead  of 
muscular  for  the  abdominal  wall  would  be  useless  however 
for  the  respiratory  act,  since  it  has  not  the  power  of  con- 
tracting and  producing  motion. 

We  cannot  regard  the  abdominal  muscles  as  being  any- 
thing more  than  passive  agents  in  preventing  the  escape  of 
the  abdominal  contents,  but  they  are  able  to  accommodate 
themselves,  owing  to  their  elasticity,  to  varying  conditions 
of  intra-abdominal  pressure.  The  normal  action  of  the 
uterus,  urinary  bladder,  or  rectum  is  independent  of  the 
action  of  the  diaphragm  or  abdominal  muscles.  When 
the  walls  of  the  abdomen  are  weakened  and  ventral  hernia 
develops — as  from  direct  injury,  poliomyelitis,  or  laceration, 
for  example  by  a  bullet,  of  the  lower  intercostal  nerves — 
this  resistance  is  weakened  or  lost.  In  cases  of  poliomyelitis 
affecting  the  abdominal  muscles,  rest  in  the  supine  position 
should  be  insisted  on,  preferably  in  a  double  Thomas's 
splint  or  a  plaster  of  Paris  casing.  The  erect  posture  should 
be  attained  slowly,  the  patient  being  gradually  elevated  in 
bed  from  the  supine  to  the  sitting-up  position  by  means  of 
pillows.  Under  this  treatment,  and  owing  also  to  the  fleshy 
nature  of  the  abdominal  muscles,  the  prognosis  of  this 
comparatively  rare  condition  is  altogether  favourable. 
Unfortunately  it  is  frequently  overlooked  in  its  early 
stage,  and  the  first  evidence  of  its  presence  may  be  bal- 
looning of  one  or  other  side  ofjthe  abdomen.      Hence 


240  THE   ACTION    OF    MUSCLES 

the  importance  in  poliomyelitis  of  insisting  on  recumbency 
at  the  outset.  It  is  worthy  of  remembrance  that  when 
Cowper,  more  than  two  centuries  ago,  first  observed  that 
the  lower  fourth  of  the  rectus  abdominis  was  uncovered  by 
tendon  sheath — having  only  the  transversalis  fascia  and 
peritoneum  dorsally — he  regarded  it  as  an  abnormality 
likely  to  lead  to  a  weakening  of  the  support  of  the  body 
wall,  "  so  that  accident  like  this  might  be  the  cause  of  certain 
ruptures."  In  inflammatory  conditions  of  the  abdomen, 
such  as  appendicitis  and  acute  peritonitis,  the  patient  will 
endeavour  to  keep  the  parts  as  immobile  as  possible  by 
bringing  more  into  play  the  action  of  the  thoracic  muscles, 
and  by  moving  the  diaphragm  in  inspiration  as  little  as 
possible.  Diaphragmatic  movement  in  these  conditions 
means  visceral  movement,  and  visceral  movement  means 
pain.  The  abdominal  muscles  on  one  or  both  sides  are 
kept  in  an  apparent  state  of  relative  rigidity  in  these  con- 
ditions, but  they  must  relax,  though  to  no  great  extent, 
for  purposes  of  inspiration.  Diminution  of  abdominal 
breathing  is  an  important  sign  of  serious  abdominal 
mischief.  It  is  on  account  of  the  reciprocal  relaxation  and 
elongation  of  the  abdominal  muscles  during  inspiration, 
that  we  ask  a  patient  to  draw  a  deep  breath  to  enable 
the  abdomen  to  be  palpated  thoroughly.  An  incision 
through  the  abdominal  wall  means  an  incision  through 
respiratory  muscles. 

Professor  Keith  regards  visceroptosis,  or  displacement  of 
abdominal  organs,  as  primarily  due  to  failure  in  the  support- 
ing power  of  the  abdominal  muscles,  and  as  a  causative 
factor  poliomyelitis  must  be  remembered.  Weakening  of 
the  abdominal  muscles  means  less  resistance  to  the  dia- 
phragm, which,  by  its  contraction,  forces  downwards  and 
forwards  the  abdominal  contents.  In  true  visceroptosis 
the  diaphragm  occupies  permanently  a  lower  or  inspiratory 
position,  and  the  abdominal  organs  are  forcibly  and  per- 
manently displaced.  Visceroptosis  is  much  more  common 
in  women  than  in  men,  and  in  women  the  breathing  would 
appear  to  be  less  abdominal  and  more  thoracic.     There  is 


THE    MUSCLES    OF    RESPIRATION  241 

little  doubt  that  this  is  associated  with  the  use  of  corsets 
and  abdominal  bands.  These,  by  their  interference  with 
free  abdominal  action,  ultimately  cause  atrophy  and  weak- 
ness of  the  abdominal  muscles  from  pure  disuse.  A  similar 
condition  is  seen  in  the  adducted  big  toe  with  bunion 
formation  due  to  atrophy  of  the  abductor  hallucis  from 
the  pressure  of  tight,  badly  fitting  boots.  Any  hospital 
physician  must  have  remarked  on  the  difference  between 
the  male  and  female  adult  abdominal  wall,  which  is  so 
frequently  in  the  latter  flabby  and  toneless. 

Hernia. — The  pressure  to  which  the  abdominal  viscera 
are  subjected,  both  by  the  action  of  the  diaphragm  as  well 
as  by  the  abdominal  muscles,  together  with  certain  altera- 
tions in  the  inguinal  region  associated  with  the  erect  posture, 
are  regarded  by  many  as  the  principal  agents  in  the  causation 
of  femoral  and  inguinal  hernia.  These  formations  would 
appear  to  be  almost  peculiar  to  man  amongst  the  mammalia. 
During  the  seventh  month  of  foetal  life  the  testes  traverse 
the  abdominal  wall  in  an  oblique  direction,  which  led  Cowper 
to  observe  that  "  the  bowels  were  prevented  from  falling 
down  by  the  obliquity  of  the  spermatic  passage."  After 
birth  the  testes  reach  the  fundus  of  the  scrotum.  Under 
ordinary  circumstances  the  processus  vaginalis  or  peritoneal 
prolongation  associated  with  testicular  descent  should  close 
after  birth,  above  at  the  internal  abdominal  ring,  and  below 
close  to  the  testes. 

According  to  Hamilton  Russell,  inguinal  hernia  in  the 
young  is  due  to  failure  in  the  upper  occlusion  ;  the  hernia 
is  not  due  primarily,  therefore,  to  straining  or  pressure, 
but  to  the  fact  that  there  is  a  congenital  sac  into  which  gut 
happens  to  have  entered.  "  No  sac,  no  hernia,"  is  Russell's 
dictum.  In  the  young,  therefore,  all  that  is  necessary 
for  cure  of  the  hernia  is  to  remove  the  sac  without  strength- 
ening the  inguinal  wall,  since  in  the  absence  of  a  sac  the 
conjoined  tendon  is  able  to  act  as  a  powerful  compressing 
agent  on  the  inguinal  canal.  This  simple  principle  has 
made  the  operative  treatment  of  hernia  in  children  almost 
a  minor  procedure.  After  nearly  twenty  years,  during 
16 


242 


THE    ACTION    OF    MUSCLES 


which  time  recurrences  could  be  watched,  it  would  appear 
to  have  justified  itself.  Still  two  questions  remain  :  why 
did  the  processus  fail  to  become  occluded,  and  why  did 
intestine  enter  it  ?  It  cannot  be  denied  that  acquired 
herniae  do  occur  in  adults  accustomed  to  heavy  weight 
lifting,  though  in  such  cases  Russell  would  say  that  there 
was  a  preformed  sac.  In  these,  if  the  hernia  were  of  old 
standing  and  the  walls  weakened  by  mechanical  action, 
he  would  not  hesitate  to  strengthen  the  canal  by  operation. 


Fig.  96. — Inguinal  region  (male  platypus). 

M,  Pectoralis  major,  p,  Pyramidalis.  r,  Rectus  abdominis,  e,  External  oblique.  In- 
ternal oblique  and  transversalis  with  attenuated  portion  corresponding  to  conjoined  tendon. 
The  muscular  external  oblique,  which  is  thrown  down,  covers  the  attenuated  area  and  is 
also  prolonged  over  parts  of  the  pyramidalis  and  rectus,  so  providing  a  muscular  barrier 
to  the  formation  of  hernia.  The  testes  are  undescended.  There  is  no  splitting  of  the  external 
oblique  indicative  of  an  external  ring. 


On  these  questions  some  interesting  light  is  thrown  by  a 
study  of  the  abdominal  wall  of  the  Australian  marsupials. 
In  the  monotremes  (platypus  and  echidna)  the  testes  are 
still  intra-abdominal,  and  the  marsupial  bone  is  present  in 
the  lower  part  of  the  ventral  abdominal  wall,  almost  as  if 
nature  were   anticipating   testicular   descent   and  seeking 


THE    MUSCLES    OF    RESPIRATION 


243 


to  improve  the  muscular  action  of  this  part.  In  the 
platypus  the  external  oblique  is  muscular  over  an  attenu- 
ated portion  corresponding  to  the  conjoined  tendon,  and 
is  also  prolonged  inwards  as  a  fleshy  muscle  over  a  portion 
of  the  superficial  (pyramidalis)   and  deep  recti.     In   the 


v«c 

Fig.  97. — Dissection  to  show  patent  internal  abdominal  ring  and  canal 
continuous  with  the  tunica  vaginalis  (male  wombat). 

A,  Portion  of  peritoneal  aspect  of  abdominal  wall  showing  internal  ring  and  cord  entering 
it.     c,  Cremasteric  muscle,     t,  Testicle,     e,  Open  testicular  sac. 

marsupials  also,  the  marsupial  bone  is  present,  and  there 
is  a  well-defined  pyramidalis  (superior  rectus)  as  well  as 
the  deep  rectus.  By  means  of  the  marsupial  bone  strength 
is  given  to  the  action  of  the  abdominal  muscles,  and  it  forms 
a  pulley  round  which  the  cremaster  runs,  passing  in  the 


244  THE   ACTION    OF    MUSCLES 

male  to  the  tunica  vaginalis-testis  and  in  the  female  to 
the  mammary  glands  at  the  back  of  the  pouch.  Muscle 
has  brought  these  extraordinary  bones  into  existence.  They 
are  not  primarily  for  the  support  of  the  prepenial  scrotum 
in  the  male,  nor  of  the  mammary  glands  and  pouch  in  the 
female,  as  is  so  often  supposed.  In  the  marsupials,  however, 
the  internal  abdominal  ring  is  patent ;  there  is  a  canal 
of  communication  between  the  abdominal  cavity  and  the 
tunica  vaginalis.  This  is  not  universal  however,  and 
herein  lies  the  interest.  The  internal  rings  in  all  female 
marsupials  I  have  examined  were  found  occluded.  It  is  open 
in  the  male  koala,  kangaroo,  wallaby,  and  wombat.  Yet 
this  patency  is  met  with  naturally  in  other  members  of 
the  mammalia,  as  for  example  in  rodentia,  in  the  males  of 
which  order  the  testes  undergo  a  periodical  increase  in  size 
during  the  rut,  and  can  pass  from  the  abdomen  into  the 
scrotum  and  be  retracted  again  into  the  belly.  In  the 
Tasmanian  devil  (carnivorous  marsupial),  there  is  occlusion 
of  the  internal  ring  in  the  male  as  well  as  in  the  female. 
In  this  animal  it  has  been  necessary  to  close  the  canal  of 
communication,  yet  in  a  saltatorial  marsupial  like  the 
kangaroo  (springing  often  25-30  feet),  with  a  lax  gastro- 
intestine,  nature  has  regarded  the  closure  of  the  internal 
ring  as  of  no  importance.  Compared  with  the  above- 
mentioned  marsupials  the  Tasmanian  devil  is  a  feeble 
muscular  type,  and  while  the  wombat  thrives  unprotected 
in  the  struggle  against  man,  the  former  is  now  almost 
extinct.  In  this  poor  type,  however,  nature  evolved  external 
genitalia  which  are  decidedly  in  advance  of  the  mono- 
tremetous  type  of  the  other  marsupials,  and  approach 
those  seen  in  the  higher  mammalia.  Comparing  the  Tas- 
manian devil  in  this  respect  and  the  wombat,  the  striking 
feature  is  the  difference  in  development  of  the  cremaster 
muscle.  In  the  wombat,  with  a  patent  processus,  the 
cremaster  is  flat,  frequently  over  1  inch  wide,  and  would 
appear  to  act  as  a  powerful  compressing  force  on  the 
attenuated  conjoined  tendon  in  its  passage  round  the 
marsupial  bone  to  the  testes.     In  the  Tasmanian  devil  the 


VCZ 

Fig.  98. — Dissection  to  show  inguinal  region  (male  Tasmanian  devil) 
(Dasyurus  sarcophilus). 

t,  Testes,  s,  Spermatic  cord.  B,  Bladder,  v.d,  Vas  deferens,  u,  Ureter,  pi,  Prostate. 
r,  Rectum,  p,  Penis,  c,  Cowper's  glands,  e,  Inguinal  region  of  abdominal  wall  (outer 
surface)  showing  epi-pubic  bone.     1,  Peritoneal  aspect  of  inguinal  region  of  abdominal  wall. 


244] 


THE   MUSCLES    OF    RESPIRATION 


245 


marsupial  bone  and  muscular  arrangements  are  similar  to 
those  of  wombat,  but  with  the  occlusion  of  the  internal  ring 
we  have  a  rounded  cremaster  with  poor  relative  develop- 
ment. Thus,  in  the  marsupials  some  vital  questions  are 
raised  concerning  the  causation  of  hernia  which  are  calling 
for  further  investigation  and  research. 


Fig.  99. — Inguinal  region  (male  wombat). 

The  external  oblique,  pyramidalis,  and  epi-pubic  bone  have  been  reflected,  r,  Rectus 
abdominis,  k,  Internal  oblique,  c,  Attenuated  area,  formed  by  conjoined  tendon,  trans- 
versalis  fascia,  and  peritoneum,  m,  Cord  with  cremaster  muscle  which  is  seen  to  be  coming 
from  internal  oblique  and  transversalis  muscles. 

If  the  diaphragm — by  its  traction  on  the  root  of  the  lungs 
and  its  impaction  against  the  abdominal  viscera  forcing 
them  down  and  so  enlarging  the  respiratory  capacity  of  the 
chest — is  the  important  factor  in  inspiration  ;  and  if  the  ab- 
dominal muscles — by  their  contraction  forcing  the  abdominal 
viscera  upwards  and  backwards  against  the  relaxed  dia- 
phragm and  so  causing  its  ascent  with  diminution  of  the 
thoracic  capacity — are  the  important  factors  in  expiration  ; 
the  thoracic  muscles,  which  are  really  part  of  the  two 
groups,  also  play  some  part  in  the  respiratory  mechanism, 
but  much  less  than  was  originally  supposed. 


246  THE    ACTION    OF    MUSCLES 

Function  of  the  Thoracic  Muscles 

The  origin  of  ribs  in  the  muscular  sheet  of  the  body  wall 
must  have  been  to  improve  muscular  action,  since  these 
allowed  the  development  of  multiplicity  of  muscles,  and 
hence  diversity  of  function.  Throughout  the  ancestral 
world  bone  is  dominated  everywhere  by  muscle.  The 
instances  of  its  subservience  are  numerous  and  scattered. 
Thus,  muscle  dominance  produces  a  broadening  of  the  bone 
surface  where  muscle  attachment  is  required,  and  a  narrow- 
ing or  rotundity  where  such  attachment  is  diminished ; 
compactness  or  lightness  of  bone  where  strength  or  other- 
wise is  requisite,  and  bony  ridges  and  projections  to  afford 
leverage. 

In  the  case  of  the  thorax,  however,  not  only  do  the  ribs 
give  attachment  to  muscle  and  protect  organs  which  are 
in  a  constant  state  of  motion  from  the  cradle  to  the  grave, 
the  heart  and  lungs,  but  they  accommodate  themselves  to 
the  motion  of  these  organs,  and  also  to  motions  of  the  body, 
such  as  forward  or  backward  movements  or  movements 
laterally.  All  this  would  be  impossible  if  we  had  plates 
of  bone  instead  of  a  number  of  movable  parts,  or  if  the 
ribs  were  completely  formed  of  bone  from  the  spine  to  the 
sternum.  Fortunately,  elasticity  and  adaptability  are 
conferred  on  the  ribs  by  the  interposition  of  elastic  and 
bending  cartilage  anteriorally  between  the  ribs  and  the 
sternum.  In  this  way  the  chest  and  its  contents  are 
rendered  almost  proof  against  blows  and  jolts  to  which  the 
body  is  liable,  and  one  has  only  to  recall  the  liability  to 
fracture  of  the  ribs  in  the  aged  in  whom  ossification  of  car- 
tilage occurs.  We  are  apt  to  imagine  that  the  thoracic  wall 
has  been  called  into  being  for  the  protection  of  the  heart 
and  lungs.  This  is  not  so.  The  testes  are  not  protected 
by  a  bony  or  cartilaginous  covering,  nor  have  the  abdominal 
muscles  ribs  in  their  interstices  for  the  protection  of  the 
gastro-intestine.  The  great  point  to  be  borne  in  mind  as 
to  their  necessity  is  the  base  they  afford  for  muscle  attach- 
ment— muscles  from  the  loins,  muscles  to  the  neck — abdo- 


THE    MUSCLES    OF    RESPIRATION  247 

minal  muscles,  and  large  muscles  like  the  pectorales, 
latissimus,  and  trapezius  for  the  movements  of  the  upper 
limbs.  When  we  find,  as  in  the  aged,  life  proceeding  with 
little  restraint  in  spite  of  complete  ankylosis  of  the  ribs 
interfering  with  their  motion  ;  it  raises  the  question  whether 
the  intercostal  muscles  will  ultimately  be  replaced  by  fibrous 
bands  between  the  ribs,  although  in  the  present  state  of 
evolution  muscles  are  a  necessity.  The  great  thoracic 
enlargement  on  inspiration  which  athletes  are  prone  to 
demonstrate  is  not,  after  all,  of  such  vital  importance  as 
is  generally  regarded.  It  is  worth  remembering  that  the 
actual  enlargement  of  the  chest  in  the  antero-posterior  and 
transverse  diameters  in  quiet  respirations  does  not  exceed 
•5  cm.  The  centre  of  motion  for  the  action  of  the  ribs  is 
at  their  articulation  with  the  spine.  There  are  two  move- 
ments— one,  elevation  or  raising  and  depression  or  falling 
anteriorally,  so  as  to  allow  increase  or  diminution  in  the 
antero-posterior  diameter  (the  vertical  being  increased  by 
diaphragmatic  action).  The  other  is  the  motion  of  the  rib 
on  its  own  axis,  which  is  a  line  drawn  between  the  two 
extremities  to  increase  or  diminish  the  transverse  diameter, 
since  by  this  motion  elevation  of  the  middle  portion  of  the 
rib  takes  place.  It  is  owing  to  the  elasticity  of  the  chest  wall 
that  these  motions  essential  to  respiration,  both  inspiratory 
and  expiratory,  can  be  carried  out.  Though,  as  stated,  the 
diaphragm  and  the  abdominal  muscles  are  the  prime  muscles 
in  respiration,  the  thorax,  through  its  muscles,  also  moves 
in  unison  with  these.  The  contraction  of  the  diaphragm  in 
inspiration  allowing  of  increase  in  the  vertical  diameter  of 
the  thorax,  is  associated  with  relaxation  of  the  abdominal 
muscles — the  tractors  of  the  thorax.  This  relaxation  also 
permits  of  the  action  of  the  intercostal  muscles,  which  elevate 
the  ribs  and  sternum,  and  thus  the  thorax  is  enlarged  in  all 
its  diameters.  In  this  they  are  assisted  by  the  levatores 
costarum,  infracostales,  and  serratus  posticus  superior — 
all  inspiratory  muscles.  With  expiration,  the  intercostal 
muscles  are  relaxed  as  well  as  the  diaphragm.  Although 
possibly  the  elastic  recoil  of  the  lungs  and  the  weight  and 


248  THE    ACTION    OF    MUSCLES 

elasticity  of  the  chest  wall  (since  the  ribs  are  always  en- 
deavouring to  maintain  the  equilibrium  between  inspiration 
and  expiration)  are  factors,  the  essential  one  in  my  opinion 
is  the  action  of  the  abdominal  muscles.  They  act  not  only 
on  the  viscera,  but  also,  owing  to  the  traction  they  exert, 
on  the  lower  half  of  the  thorax  ;  in  this  they  are  assisted 
by  the  triangularis  sterni.  This  muscle  is  a  continuation 
up  of  the  transversalis  abdominis,  and  its  action  is  to 
depress  the  ribs,  draw  down  the  costal  cartilages,  and  so  to 
act  as  a  muscle  of  expiration.  It  is  questionable  whether 
the  serratus  posticus  inferior  has  any  respiratory  function. 
Probably  Riolan  was  right,  centuries  ago,  when  he  regarded 
this  muscle  as  a  binding  and  strengthening  force  to  the 
muscles  of  the  back,  similar  to  the  annular  ligaments  at 
the  ankle.  There  is  little  doubt,  as  Haller  taught,  that  the 
internal  intercostals  are  not  expiratory  muscles,  but  that 
both  sets  are  inspiratory.  The  division  of  the  intercostals 
into  two  sets  is  really  artificial,  for  it  is  a  mechanical 
arrangement  by  which  nature  obtains  velocity  of  action 
at  the  expense  of  power.  As  in  the  case  of  the  abdomen, 
a  single  straight  sheet  of  muscles  between  the  ribs  would 
be  insufficient.  By  the  obliquity  of  the  intercostals  we 
have  traction  through  the  maximum  space  with  the 
minimum  contraction.  Through  this  arrangement  less 
muscular  effort  is  required  to  approximate  the  ribs.  The 
action  of  the  intercostal  muscles,  which  we  must  remember 
are  essentially  muscles  of  ordinary  inspiration,  would 
appear  to  be  as  accessories  in  connection  with  forced  in- 
spiratory efforts  as  in  running  or  violent  bodily  exercise  ; 
efforts  which  are  impossible  in  old  age,  when  thoracic 
elasticity  is  greatly  diminished  or  absent.  In  violent 
exercise  intercostal  action  is  necessary  as  an  aid  to  the 
action  of  the  diaphragmatic  pump,  so  as  to  permit  of  the 
rapid  aeration  of  the  blood  essential  to  the  effort. 

Phrenic  Paralysis. — Only  once  have  I  seen  a  case  of 
paralysis  of  the  diaphragm  (post-diphtheritic),  and  it  was 
interesting  to  note  that  the  thoracic  muscles  failed  as 
inspiratory  agents  to  compensate  adequately  for  the  impair- 


THE    MUSCLES    OF    RESPIRATION  249 

ment  of  diaphragmatic  action.  Aeration  was  defective, 
there  was  little  abdominal  movement,  the  lungs  were  in- 
completely emptied,  congestion  of  the  bases  followed,  with 
subsequent  consolidation  and  gangrene.  In  these  rare 
cases  it  is  presumably  a  '.'  paresis,"  not  a  "  paralysis,"  of 
the  diaphragm  that  is  present.  With  paralysis  of  the 
diaphragm  it  is  inconceivable  that  life  can  be  prolonged.  If 
both  phrenic  nerves  (the  main  motor  nerves  of  the  dia- 
phragm) be  divided,  death  results — the  other  inspiratory 
muscles  being  unable  to  maintain  respiration  effectively. 

Epigastric  Retraction. — Associated  with  the  dyspnoea 
of  a  severe  case  of  laryngeal  diphtheria  is  the  so-called 
"  epigastric  retraction,"  which  is  an  indication  for  immediate 
intubation  by  O'Dwyer's  tubes  or  for  tracheotomy.  The 
inspiratory  muscles,  namely  the  diaphragm  and  intercostals, 
are  working  ineffectively.  Owing  to  the  diminished  entrance 
of  air  into  the  lungs  through  the  mechanical  obstruction 
of  the  larynx,  the  expansion  of  the  thorax  and  lungs  is 
at  a  minimum.  There  is  little  downward  and  forward 
movement  of  the  abdominal  viscera.  The  lessened  pres- 
sure within  the  thorax,  owing  to  the  diminishing  entrance 
of  air,  is  insufficient  to  counteract  the  pressure  of  the  outside 
atmosphere,  and  supraclavicular,  epigastric,  and  intercostal 
compression  result.  The  pressure  within  and  without  the 
thorax  is  unevenly  balanced. 

If  there  were  complete  obstruction  to  the  entrance  of  air 
into  the  lungs,  no  expansion  of  the  thoracic  cavity  could 
occur,  the  muscles  of  inspiration  being  unable  to  counter- 
act the  atmospheric  pressure  on  the  outside  of  the  chest. 


INDEX 


Abdomen,  inflammatory  conditions 
of,    movement   of  thoracic  at 
expense  of  abdominal  muscles 
in,  240 
Abdominal  muscles,  228 

comparative  anatomy,  237,  238 
development,  238 
function,  237,  247 

modification  in,  238 
in  platypus,  230 

poliomyelitis  affecting,  rest  treat- 
ment, 239 
relaxation,  associated  with  con- 
traction of  diaphragm,  247 
relaxed  and  stretched,  action  of, 
in  respiration,  stimulus  to,  234 
support  of  viscera  by,  239 
Abdominal   and   thoracic   muscles, 
action  of,  234 

respiratory    movements    effected 
by,  234 
Abdominal    organs,    effect .  of    dia- 
phragm on,  236 
ribs  in  crocodile,  231 
ring,  internal  occlusion  in  female 
marsupials,  244 
potency  in  marsupials,  243,  244 
viscera,   respiratory  movements, 

236 
wall,  muscles  of,  228 
Abduction,  application  in  paralysis 
of  quadriceps,  162 
essential  movement  of,  46 
or  adduction  frame,  140 
splint,    upper    limb,    advantages 
of,  227 
description,  59 

in  loss  of  muscular  power  of 
deltoid,  and  trapezius,  58,  59 
in   musculo- cutaneous   paraly- 
sis, 80 
in  separation  of   epiphysis  of 
humerus,  227 
Abductor      hallucis,      origin      and 
insertion,  185 
weakened  state  in  hallux  valgus, 
187 


Abductor    minimi    digiti,     action, 

origin  and  insertion,  191 
Abductor  pollicis,  99 

and    adductor    hallucis,    actions 
contrasted,  186 
Abductors  of  little  finger,  97,  98 
Acrobats,  best  illustration  of  action 
of    flexors    and    extensors    of 
ankle  seen  in,  176 
muscular  feats  of,  150,  212,  216, 
217,  218 
Acromion,  action,  57 
Adductor  brevis,  origin  and  course, 
136,  138 
contraction,  result,  68 
hallucis,  oblique  portion  of,  185 
transverse     portion     of,     185, 
186 
longus,  origin  and  course,  136 

and  magnus,  work  of,  139 
magnus,  insertion,  138,  139 

origin,  136 
of  little  finger,  98 
Adductores  pollicis,  98,  99 
Adductors,  action  on  thigh,  139 
spasmodic  contraction  in  spastic 
diseases  in  children,  140 
surgical  treatment,  140 
Adhesions,  breaking  down  of,  27 
African  races,  os  calcis  in,  171 
Albinus,  biventer  cervicis,  203 
distinction       between       splenius 
capitis  and  splenius  colli,  202 
Aluminium  cock- up  splint  in  gra- 
duation of  flexion  in  musculo- 
spiral  paralysis,  121 
Amphibia,   abdominal  situation  of 
lungs  in,  235 
muscles  of  body  wall  in,  237 
Anconeus,    order   and   position    of 

origin,  in 
Ankle-joint,    diseased    or    injured, 
rest  of,  224 
extension     backward     of     rigid 

body  at,  175,  176 
flexion  and   extension   at,    prin- 
ciples of  leverage  in,  174 


251 


252 


INDEX 


Ankle-joint,   flexion  at,   in  talipes 
calcaneus,  176 
flexors  of,  paralysis,  23 

shortening  of,  27 
flexors  and  extensors,  best  illus- 
tration of  action,  176 
maintenance    of   equilibrium   at, 
in  respect  of  flexion  and  exten- 
sion,   in    deformities    of    foot, 
192,  193 
position  for  rest  or  recovery,  or 
for  ankylosis,  224 
Ankylosis  of  joints,  222,  223,  226, 
227 
prevention    in    upper    extremity 
more  important  than  in  lower, 
223 
Annuentes,  203 

Anthropoids,  deltoid  function  in,  1 7 
dependence  upon  fore   limb  for 

support,  161 
femur  in,  136 
peroneus  brevis  iri,  181 
Ape,  orthograde  posture  of,  17 

quadriceps  in,  161 
Appendicitis,  movement  of  thoracic 
at  expense  of  abdominal  mus- 
cles in,  240 
Arc      shoe      attached      to      single 
Thomas's    splint    for    rest    of 
knee-joint,  225 
in  deformities  of  foot,  197,  198 
Arc   splint,    use  in  rest  of  ankle- 
joint,  224 
Arcuate   ligaments   of   diaphragm, 

232 
Arm,     abduction    of,     in    loss    of 
muscular  power  of  trapezius, 

58 
ability  to  raise,  in  man,  50,  51 
elevation,     to    rest    triceps,     in 
musculo-spiral  paralysis,  117 
Athletes,    bending    back    of    rigid 
trunk  and  thigh  at  knee-joints 
by,  150 
extension    backwards     of     rigid 
body  at  ankle-joint  in,  176 
Atlas  and  occiput,  articulation  be- 
tween,   flexion   and   extension 
at,   example  of  first  order  of 
leverage,  205 
articulation  with  axis,  200 
with  occiput,  201 
Axis,      direct      connection      with 
occiput,  201 

Back  and  loins,    muscles   moving, 
213 

dorso-vertebral,    or    extend- 
ing, 214 


Back- splint  and  foot- piece  in  rest 
of  foot,  in  paralysis  following 
injury     of    internal    popliteal 
nerve,  195 
Balance,   uneven,   between  elonga- 
tion and  contraction,  39 
Bandage     sling,     use     in     loss     of 
muscular  power  of  serratus,  60 
Bartholin,    relations    between    dia- 
phragm and  transversalis,  232 
Bell,  Sir  Charles,  source  of  muscular 

action,  161 
Biceps  brachii,  action,  75 

brachialis  compared  with,  71 
in  Malabar  squirrel,  78,  79 
in  wombat,  78,  79 
insertion,  75 

long   head    of,    division   avoided 

during  excision  of  shoulder 

joint,  75 

involvement    in    diseases    and 

injuries     of     shoulder- j  oint, 

79 
position    of    rest    in    musculo- 
cutaneous paralysis,  80 
origin,  73 

paralysed,    old    cases   with    con- 
tracted pronator  teres,   treat- 
ment, 83 
recovery,  how  effected,  82,  83 
state  of,  in  pronation  and  supina- 
tion of  forearm,  76 
supination,  78 
Biceps  cruris,  heads  of  origin,  148 
in  monotremes  and   marsupials, 

152 
insertion,  148 
of  platypus,  134,  135 
outward  rotator,  151 
portion  in  gorilla  more  distinct 
than  in  man,  153 
Biventer  cervicis,  203 
Bland-Sutton,   Sir  J.,   Gimbernat's 
ligament  and  triangular  fascia, 
230 
Body,      human,     falling     forward, 
muscles  preventing,  218 
superincumbent  pressure  of,  how 

supported,  159 
trunk  of,  point  at  which  upper 
extremity  connected  with,  57 
relation     of     limb     action     of 
upper  extremity  to  rigidity 
of,  234 
upright  position,  muscles  neces 

sary  for  maintaining,  175 
wall,     muscular    system    of,    in 
amphibians,  237 
Bone,  insertion  of  muscle  into,  3 
relation  to  muscle,  4 


INDEX 


253 


Boot,  shape  of,  in  cases  of  hallux 

valgus,  187 
Brachialis,  antagonist  of,  71 

character  in  man,  71 

compared  with  biceps,  71 

function,  71,  72,  75,  76 

how  rested  in  musculo- cutaneous 
paralysis,  80 

"  moment  of  force  "  of,  80,  81,  82 

origin  the  insertion,  and  insertion 
origin,  72 

paralysis  of,  test  for,  9 

reverse  action  of,  72 

stimulus  to  contraction  of,  41 
Brachio-radialis,  action,  73 

in  marsupials,  73 

origin  and  insertion,  73,  111 

"  survival  value  "  of,  34 
Bundles.     See  Fasciculi 
Bunion  of  big  toe,  186 

Calcaneus.     See  Os  calcis 
Caliper  splint,  Thomas's,  for  knee 
joint  after  commencement  of 
ambulation,  226 
Cardboard,   powdered,   use  of,   for 
rest  of  paralysed  limbs,  60,  65, 
80,  120,  123 
Cervical  region,  flexion  and  exten- 
sion, movements  free  in,  206 
rib,  31,  32 
Cetacea,  diaphragm  in,  232 
Children,  inguinal  hernia  in,  241 
operative  treatment,  241 
spastic  diseases  in,   impediment 
to  walking  in,  140 
paraplegia   of,    contraction   of 
gracilis  in,  148 
Cock- up    splint,   for    rest  of  wrist 

joint,  118,  119,  226 
Complexus,  action,  202,  203 
origin  and  insertion,  202 
Connective  tissue,  2 
Conoid,  57 

Contracted  muscle,  22 
Contraction,  chronic,  22,  24 

deformities  produced  by,  25 
treatment  of,  26 
mechanism  of,  46 
physiological  action  of,  36 
stimulus  to,  40 

uneven  balance  between  elonga- 
tion and,  39 
Contractions,  breaking  down  of,  27 
Coraco-brachialis,  55 
Coraco- clavicular  ligaments,  57 
Cornual  cell,  rest  of,  19 
Costalis  cervicis,  206,  207 
Cowper,     abnormality     in     rectus 
abdominis,  240 


Cowper,     comparative     weight     of 
extenders  and  benders  of  knee, 

159 
discoverer  of  inter-spinales,  209 
Cremaster    muscle    in    Tasmanian 

devil  and  wombat,  244 

Crocodile,  abdominal  ribs  in,  231 

Crureus  (vastus  intermedius),  155 

connection  of  vastus  internus  or 

medialis  with,  154,  155 

Death,   elasticity  not  affected  by, 

38 
Deformities    produced    by    chronic 

contractions,  25 

Deltoid,  52,  53,  54,  57 

abduction,  movement  in  arc  of, 
61,  62,  64,  65 

action  of,  14 

characteristics  of,  51,  52 

development  in  man,  51 

function,  45,  57 

in     anthropoids     and     marsu- 
pials, 17 

insertion,  54 

loss     of     muscular     power     in, 
position  of  rest  for,  59 

origin,  52 

paralysed,  point  of  support  of,  2 1 
re-education,  62,  63,  64 

paralysis  of,  23 
test  for,  30 
Diaphragm,    arcuate  ligaments  of, 
232 

comparative  anatomy,  232,  235 

contraction  associated  with  re- 
laxation of  abdominal  muscles, 
247 

crura  of,  232 

dimensions,  231 

direct  antagonists  of,  237 

effect  on  abdominal  organs,  236 

function,  235,  247 

inequality  of  action  between 
right  and  left  sides,  237 

movement  of,  avoided  in  ab- 
dominal inflammatory  condi- 
tions, 240 

muscles  of,  231 

paralysis,  rarity,  248,  249 

periphery,  231 

principal  muscle  of  inspiration 
and  respiration,  234 

upper  and  lower  surfaces,  231 
"  Dropped  toe  "  deformity,  183 
"  Dropped    wrist,"     definition    of, 
119 

metal  splint,  Thomas's,  118 

prognosis,  test  for,  119 

treatment,  ng 


254 


INDEX 


Elastic  body,  action  compared  with 
muscular  action,  38 
movement  by  shortening,  38 
Elastic  power,  1 

Elbow  joint,   diseased    or    injured, 
rest  of,  angle  of  flexion  for, 
227 
best  position  for,  226,  227 
wrong  methods  for,  226 
extension,  how  best  effected,  77 

to  rest  triceps,  117 
flexion    of,     differentiated    from 
supination     of     forearm     in 
marsupials,  79 
in  ulnar  paralysis,  10 1 
how  best  effected,  77 
how  permitted,  77 
in  musculo-cutaneous  paralysis, 
80 
not  position  of  physiological 
rest,  80 
flexor  of,  75,  76 
forces  acting  on,  41 
muscle  crossing,  70 
Elongation,  rnuscular,  as  mechani- 
cal action,  37 
power  of,  38 

uneven    balance    between    con- 
traction and,  39 
Epigastric  reaction,  249 

treatment,  249 
Epi-pubic  or  marsupial  bone,  230 
Equilibrium  muscular  production,  39 
Erect  posture,  4,  16 

in  man,  characteristics  of,  49,  50 
Erector  spinae,  action  of,  216 
Erectores   spinae,    action,    extreme 
instance  in  acrobats,  216,  217 
antagonists  of,  218 
contraction,  218 
position  and  attachment,  214 
European  races,  os  calcis  in,  171 
Evolution  in  relation  to  function  of 
quadriceps,  160,  161 
muscle  function  in,  17 
of  muscular  action,  14 
Extensor  brevis  digitorum,  fulcrum, 

183 
insertion  of  tendons,  182,  183 
muscular  bellies  of,  188 
origin  and  course,  182,  188 
tendons  of,  188 
Extensor  brevis  pollicis,  112 
Extensor  carpi  radialis  brevis,  111 
longus,  in 
carpi  ulnaris,  111,  112 
communis  digitorum,  in,  112 
action  of,  114,  115 

metacarpophalangeal  joints, 
1*6 


Extensor      communis      digitorum, 
origin,  114 
tendons  of,  114 

testing  for  recovery  of,  in  mus- 
culo-spiral  paralysis,  121 
indicis,  112 
longus     and     brevis     digitorum, 

special  function  of,  189 
longus  digitorum,  184,  188 

tendons  of,  188 
longus  hallucis,  action,  183 
fulcrum,  183 

held  down  by  ligaments,  184 
insertion  of  tendon,  182 
origin,  182 
longus  pollicis,  100,  112 

insertion  of,  112 
minimi  digiti,  in,  112 
ossis  metacarpi  pollicis,  112 
rest  in  musculo- spiral  paralysis, 
117 
tendon,  movement  over  condyles 
of  femur,  155 
Extensors,  action  of,  39 

of  fingers,  order  and  position  of 
origin,  in,  112 
re-education  in,  107,  108 
of  foot,  170 
of  leg,  154 

stimulus  to  contraction  of,  40 
External      oblique      (descendents), 
aponeurosis  of,  228,  229 
fleshy  muscle  of,  228 
muscle  fibres  of,  228 
situation,  228 
Extremity,    upper,    adequate   fixa- 
tion of  one  joint,  how  best 
secured,  227 
limb     action     in    relation     to 

rigidity  of  trunk,  234 
paralysed,  re-education  in  in- 
fantile paralysis,  65,  66 
prevention     of     ankylosis    in, 
more     important     than     in 
lower,  223 

Fasciculi,  muscular,  2 
Femur,  body  weight  when  standing 
shared  by  each,  130 

condyles  of,  movement  of  ex- 
tensor tendon  over,  155 

in  anthropoids,  136 

middle,  body-weight  transmitted 
through,  when  standing  on  one 
leg,  130 

movements  of,  127 

muscles  performing,  127 
where  performed,  127 

neck  of,  dimensions,  why  neces- 
sary, 30 


INDEX 


255 


Femur,    rotatory    movements    of, 

when  impossible,  144 
Fibre,  elastic,  elongation  of,  38 
Fibres,  cylindrical,  1 
direction  of,  13 
elongated,  tightening  of,  27 
tension  of,  47 
Fibro- cartilage,    formed  in  tendon 

of  peroneus  longus,  173 
Fibrosis,  luetic,  28 
Fibula,  adaptive  changes  in,  31,  32 
compared  with  tibia,  17 
congenital  defects  of,  treatment, 

178,  179 
non-existence   as   separate   bone 
in  kangaroo,  178 
Finger,  dorsum  of,  arrangement  of 
motor  forces  on,  115 
little,  small  muscles  of,  nerve  sup- 

p!y>  97 

middle,    double    supply    of    pro- 
fundus tendon  to,  108 
Fingers,   abduction  and  adduction 
of,  99,  100,  101 

condition  of,  in  partial  ulnar 
paralysis,  109 

extension  in  musculo- spiral  par- 
alysis, 117 

extensors  of,  order  and  position 
of  origin,  in,  112 
re-education,  107,  108 

flexion  favoured  by  position  of 
extension  of  wrist,  in  ulnar 
paralysis,  109 

flexion  of,  recovery  in  median 
nerve  paralysis,  re-education 
for,  95 

flexor  leverage,  improvement  by 
extending  wrist,  96 

flexors  of,  85,  87,  90 

lateral  action,  imaginary  line  for, 
191 

middle  and  index,  double  nerve 
.  supply,  107 

movements  in  median,  ulnar, 
and  musculo- spiral  paralysis, 
124-6 

muscles  of,  re-education  in  ulnar 
paralysis,  104 

rest  of,  in  re-education  of  inter- 
ossei,  108 

weakened,  in  musculo- spiral  par- 
alysis,   extension,   how   aided, 
121 
Flat  foot,  187 

Fleshy      muscles,      stability      and 
strength  of,  3 

nature  of  muscle,  3 
Flexor  accessorius,  function,  189 

origin  and  insertion,  189 


Flexor  brevis   digitorum    (perfora- 
tus),  action,  190,  191 
tendons  of,  190 
Flexor  brevis  hallucis,  tendons  of, 

184 
Flexor  brevis  minimi  digiti,   func- 
tion, 190 
origin  and  insertion,  190 
Flexor  brevis  pollicis,  98 
Flexor  carpi  ulnaris,  10 1 
nerve  supply,  97 
origin,  97 
communis,  antagonists,  89 
longus      digitorum      (perforans), 
action,  190,  191 
insertion  of  tendons,  189 
origin  and  insertion,  189 
Flexor  longus  hallucis,  use  of,  185 

origin,  184 
Flexor  profundus,  tendons,  87,  88 
and    flexor    sublimis,    reciprocal 
leverage  by,  to  improve  flexion 
power,  88 
digitorum,  origin,  97 
nerve-supply,  97 
Flexor  sublimis,  tendons,  87,  88 
Flexores  capitis,  205 
Flexors,  action  of,  39 

contracture  of,  in  musculo-spiral 
paralysis,  118,  120,  124 
division  of  lumbricales,  124-6 
examples  of  pulleys,  9 
of  ankle,  paralysis  of,  23 

shortening  of,  27 
of  fingers,  85,  87,  90 
of  foot,  168 

of  knee,  chronic  shortening  of,  23 
of  leg,  146 

antagonist,  158 
of  wrist,  testing  of,  29 
reverse  action  of,  5 
Food,    stimulus  to   intestinal   con- 
traction, 38 
Foot  and  hand,    specialization  of, 
function  in,  compared,  192 
and    toes,     muscles    acting    on, 
rest  and  re-education  in  sciatic 
nerve  paralysis,  192,  194,  195 
deformities,  acquired,  179 
following  poliomyelitis,  176 
maintenance  of  equilibrium  at 
ankle  as  regards  flexion  and 
extension  in,  192,  193 
surgical  treatment,  197 
useful  form  of  splint  for,   197, 
198 
dorsal   and   plantar   surfaces   of, 
impairment  of  function,   how 
produced,  193 
eversion,  179 


256 


INDEX 


Foot    eversion   in    kangaroo,    how 
prevented    178 
with  extension,  muscle  produ- 
cing, 177 
with  flexion,  muscles  producing, 
177 
extension,  muscles  effecting,  170, 

173 
flexion,    muscles    effecting,    168, 

173 

front  of,   action,   how  strength- 
ened, 186 

human,    eversion    and   inversion 
of,  17 

interossei  in,  191 

inversion,  177 

with    extension,    muscle    pro- 
ducing, 177,  194 
with  flexion,    muscles   produ- 
cing, 177 

inverters  and  everters,  action  of, 
197 

inversion  and  eversion  in  flexed 
and    extended    position,    in 
connection       with       lateral 
movements,  197 
in  koala,  178 

maintenance   at  right   angle,    in 
prevention     of     deformities, 
197 

muscles  acting  on,  168-81 

of  kangaroo,  32 

of  koala,  33 

rest  treatment  in  case   of  shell 

wound  of  upper  leg  involving 

peroneal  nerve,  193,  194 

in    paralysis    following    injury 

of  internal  popliteal  nerve, 

*95 

right,  "paralysis"  following  in- 
fantile paralysis,  recovery  from 
after  rest  and  re-education  of 
muscles,  195,  196 

splint,  special  form  useful  in 
treatment  of  deformities,  197, 
198 

"  springiness  "  on,  importance  of, 

185 
Forearm,  branches  of  ulnar  nerve 
arising  in,  97 
flexors  of,  test  for  action,  29 
ischemic  "  paralysis  "  of,  avoid- 
ance, 227 
paralysis  of  pronators,  23 
position  of,  in  testing  for  deltoid 
recovery  or  in  commencing  re- 
education, 63 
position    of    over- supination    in 
musculo-cutaneous     paralysis 
§9 


Forearm,  position  to  secure  rest  in 
musculo- spiral  paralysis,  117 
pronation     and     supination     of, 
state  of  biceps  in,  76 
in  flexed  position,  how  effected, 

77 
supination  of,  differentiated  from 
flexion  of  elbow  in  marsu 
pials,  79 
how  effected,  77 
Fore- limb,  ability  to  raise  in  mar- 
supials, 51 
as  means  of  support,  17 
dependence  of  anthropoids  upon, 
for  support,  161 
Fracture  of  patella,  production  by 

quadriceps,  159 
Fulcrum,  definition,  39 
Function  (muscle),  evolutionary  law 
of,  17 
(muscle),  re-education  of,  20,  22 
specialization  of,  44 

Gastrocnemius,  course,  171 
function  of,  173,  174,  175 
origin  and  insertion,  170 
reverse  action  of,  42 
tendons  of,  170 
Gemellus,     superior     and     inferior 
origin,  142 
insertion,  142 
Gimbernat's  ligament,  230 
Gluteus  maximus,  action  in  rising 
from  sitting  to  erect  posture, 

!34 
functions  of,  134 
of  platypus,  134,  135 
origin  and  tendinous  insertion,  141 
relaxation  and   elongation,    129, 

149 
relaxation    with    contraction    of 

ilio-psoas,  effect,  158 
size  in  man,  131,  132 
Gluteus  medius,  action  of,  141 

muscle  assisting,  141 
Gluteus  minimus,  action  of,  144 
origin  and  insertion,  134,  144 
Gorilla,  erect  posture,  136 

portion  of  biceps  cruris  in,  153 

Gracilis,     contraction     in     spastic 

paraplegia  of  children,  148 

development  in  platypus,  151 

fulcrum  of,  147 

origin,  insertion,  and  function, 
146,  147,  148,  151 
Grafting  in  paralysis,  18 
Gunshot  wound  of  great  sciatic  or 
peroneal  nerves,  cause  of 
"  paralysis  "  of  leg  and  foot 
muscles,  193 


INDEX 


257 


Hall,    Marshall,    reflex    movement 

from  irritation,  161 
Hallux,  muscles  on,  182 
Hallux  valgus,  187 

operation  in  severe  cases,  187 
reason  for  greater  frequency  in 

women,  187 
shape  of  boot  to  be  worn  in  cases 

of,  187 
treatment,  187 

weakness    of    abductor    hallucis 
in,  187 
Hamstrings,    true    cause    of    tight 

feeling  of,  149 
Hand,    branches    of    ulnar    nerve 
arising  in,  97 
radial    or    ulnar    deviation,    re- 
education for,  114 
rest    of,    in    paralysis    of    wrist 

extenders,  118 
and  foot,  specialization  of  func- 
tion in,  compared,  192 
Hand-piece,    application    in    ulnar 

paralysis,  103 
Hand  splint,  Thomas's,  for  rest  of 

wrist  joint,  226 
Head,  lateral  movement,  212 
movements  on  spine,  201 
muscles  moving,  200 
Hernia,  femoral,  cause,  241 

in  children,  operative  treatment 

easy,  241 
inguinal,  cause,  241 

in  children,  cause,  241 
ventral,  development,  239 
Hip- joint,  adduction  and  abduction 
at,  136 
alteration  of  angle  at,  151 
disease,     psoas     contraction     as 

diagnostic  of,  132 
flexion  at,  130 

during  sitting,  150 
how  effected,  130,  158 
and   extension  of,    effects    on, 
spine,  132 
forcible  reduction  of,  133 
rotatory  movements  at,  limited, 

144 
subject  of  more  continuous  move- 
ment than  other  joints,  129 
and  knee  joint,  flexions  of,  146 
independent  movements,    146, 

J47 
Horizontal  bar,  elevation  of  body 
on,  example  of  reverse  action 
of  brachialis,  72 
Humerus,     check     on     movement 
upward,  57 
muscles  moving,  52 
insertions  of,  53 

17 


Humerus,  rotation  of,  58 

separation  of  epiphysis  of,  treat- 
ment, 227 

Iliacus,  origin  and  insertion,  130 
Ilio-costalis,   course  and  insertion, 

214 
Ilio-psoas,  131 

action  of,   in  movement  of  leg, 
in    recovery     of    paralysed 
quadriceps,  165,  166 
when  body  bent  forward  at  hip 
joint,  149 
contraction,    with   relaxation   of 
gluteus  maximus,  effect,  158 
Index  and  middle  fingers,  interossei 

of,  double  nerve  supply,  107 
Inferior  oblique,  action,  204 

course,  204 
Inflammation,  rest  the  basic  treat- 
ment of,  19,  21 
Inflammatory  conditions  of  abdo- 
men,   movement    of    thoracic 
muscles  in,  240 
Infracostales,  233 
Infraspinatus,  origin  and  insertion, 

54 
Inguinal  region  in  male  platypus, 
242 
in  male  wombat,  245 
Injury,  muscle  rest  after,  20 
Insertion  of  muscle,  2,  5 

adaptation  to  alteration  of  dis- 
tance, 43 
Inspiration,  principal  muscle  of,  234 
Intercostal  muscles,  action,  247,  248 

fixed  point  for  action  of,  213 
Intercostals,  external,  232,  233 

internal,  233 
Internal  oblique  (ascendens),   apo- 
neurosis of,  229 
insertion,  229 
situation,  229 
Interossei,  action,  90 

tests  bearing  on,  100 
long  tendons  of,  10 1 
Interossei  in  foot,  dorsal,  191 
action,  192 
plantar,  191 
action,  192 
Interossei  in   hand  and   foot,    im- 
portance compared,  191 
Interossei    of    index    and    middle 
fingers,  double  nerve  supply,  107 
Interossei,  palmar,  function  of,  99 
and  dorsal,  98 

functions  of,  98,  99 
recovery  of,  in  ulnar  par- 
alysis, 106 
testing  for,  121 


258 


INDEX 


Interossei,    re-education,    point    to 
be  observed  in,  108 
on  splints  in  ulnar  paralysis, 
method,  no 
rest  of,  in  musculo-spiral  paraly- 
sis, 117 
neglect     in     ulnar     paralysis, 
results,  no 
weakness  in  ulnar  paralysis,  104 
Interosseous     muscle     contraction, 

result  of,  101 
Interphalangeal      joint,      first      or 
proximal,  flexion  at,  effect  en 
distal  phalanx,  100 
Interphalangeal    joints,    extension 
at,  100 
in  partial  ulnar  paralysis,  109 
inability  to  extend  at,  in  ulnar 
paralysis,  104,  105 
recovery  of  power,  105,  106 
Inter-spinales,  215 
action,  209,  217 
discoverer  of,  209 
Inter- transversales,  215 
action,  209,  217 
area  of  extension,  208 
region  where  best  developed,  208, 
217 
Intubation  in  epigastric  reaction,  2  49 
"  Irreparable  damage,"  15 
Ischaemic  paralysis,  28 

of  forearm,  avoidance,  227 

Joint,  muscular  opponents  of,  40 
Joints,  ankylosis  of,  222,  223,  226, 
227 
diseased,  treatment  by  counter- 
action of  active  and  passive 
forces,  222,  223 
treatment  by  perfect  rest,  222, 
223 
results  aimed  at  in,  223 
dominated     by     muscles    acting 

across  them,  222 
fixation  of,  anatomical  considera- 
tions in,  222-7 
functions,  222 
relation  of  ligaments  to,  7 
relation  to  muscle,  4 
several,  muscles  passing  over,  43 
Jumping,     muscles    employed    in, 
174,  180 

Kangaroo,  ability  to  raise  fore- 
limb  in,  51 

absence  of  tibialis  posticus  in,  178 

brachio-radialis  in,  73 

buttock,  thigh,  and  outer  leg, 
dissection  showing,  137 

erect  posture  in,  51,  131,  132 


Kangaroo,  foot  and  leg  of,  32 
function  of  sartorius  in,  152 
great    size    of    psoas    minor    in, 

131 

length  of  tendo-achillis  in,  24 
muscular  system  of,  4 
non-existence  of  fibula  as  separ- 
ate bone,  in  178 
peroneus     longus     almost     non- 
existent in,  181 
saltatorial,    eversion   of   foot  in, 
how  prevented,  178 
tibialis  anticus  in,  178 
tibia  and  fibula  in,  compared,  17 
Keith,     A.,     F.R.S.,     comparative 

anatomy  of  diaphragm,  235 
Knee  joint,  chronic  disease  of,  with 
backward    displacement,    out- 
ward rotation  of  joint  in,  151 
crossed  by  gastrocnemius,  171 
diseased  or  injured,  position  for 
rest  or  ankylosis,  225 
rest  of,  splint  for,  225 
splint    for,     after    commence- 
ment of  ambulation,  226 
dissection  of  inner  side  in  wom- 
bat, 152 
extenders  and  flexors' of,  weight 

compared,  159 
flexion  at,  how  constituted,  150 
of  rigid  body  at,  216,  217 
and  extension  in  re-education 
of  paralysed  quadriceps,  165, 
166,  167 
flexors  of,  action,  151 
how  evidenced,  150 
chronic  shortening,  23 
not  crossed  by  soleus,  171 
protection  of,  155 
rotation  inward  at,  151 
movement  at,  151 
outwards  at,  151 
stiffening   of,   to   maintain   erect 

posture,  how  effected,  50 
and  hip  joint,  flexions  of,  146 
independent  movements,  146, 

J47 

Knee  joints,  bending  back  of  rigid 
trunk  and  thigh  at,  by  acro- 
bats and  athletes,  150 

Koala,  ability  to  raise  fore- limb  in, 

51 
brachio-radialis  in,  73 
deltoid  function  in,  17 
foot  and  leg  of,  33 
inversion    and    eversion    of    foot 

in,  178 
peroneus  brevis  in,  181 
strength    of    semi-membranosus 

and  semi-tendinosus  in,  151 


INDEX 


259 


Lateral  rolling,  how  produced,  219 
Latissimus  dorsi,  origin  and  inser- 
tion, 54,  55 
Leg  and  foot,  muscles  of,  causes  of 

"  paralysis  "  in,  193 
Leg,  extensors  of,  145,  154 

flexion  and   extension   on  thigh 

when  sitting,  150 
flexors  of,  145,  146 
movement    of,     action    of    ilio- 
psoas muscle  in,  in  recovery  of 
paralysed  quadriceps,  165,  166 
muscles  acting  on,  145-67 
of  kangaroo,  32 
of  koala,  33 

upper,  shell  wound  of,  involving 
peroneal  nerve,  incapacity  re- 
sulting from,  193 
Levatores    costarum    or    supracos- 
tales,  origin  and  insertion,  233 
Leverage,  first  order  of,  205 
Levers,  examples  of,  12 
Ligaments,  elastic  properties  of,  38 
lateral,  patellar,  155 
of  extensor  longus  hallucis  and 
extensor  longus  digitorum,  184 
relation  to  joints,  7 
shortening  of,  24 
Limb,  right  lower,  supporting  trunk 
in  erect  position,  128 
upper  elevation, mechanism,  57, 58 
inutility  in  infantile  paralysis, 
cause,  91 
Limbs,  lower,  of  man,  how  differing 
from  those  of  other  mammals, 
130 
paralysed,   require  gentle  hand- 
ling, 60 
Linea  alba,  228,  229,  230,  231 
Lineae  semi-lunares,  231 

transversa,  231 
Lister's  splint.     See  Splint,  Lister's 
Loins.     See  Back  and  loins. 
Longissimus  dorsi,  attachment  and 

•insertions,  214,  215 
Longus  colli,  action,  209,  2X1,  212 
area  of  extension,  209 
three  divisions  of,  209 
Luetic  fibrosis,  28 
Lumbar  region,  flexion  and  exten- 
sion free  in,  206,  213 
flexion  or  extension  at,   results, 

219 
inter- transversales  well  developed 

in,  217 
lateral  movement  at,  213,  219 
rotation  absent  in,  213 
semi-spinales  not  found  in,  217 
Lumbricales,  origin,  190 
digital,  action,  89,  90 


Lumbricales,digital,  not  extensors  of 

middle  and  distal  phalanges,  90 
origin  and  insertion,  89 

division,  in  musculo-spiral  par- 
alysis with  contracture  of 
flexors,  124 

inner,  98 

relaxation     and     elongation     in 
musculo-spiral  paralysis,  117 
Lungs,      abdominal     situation     in 
amphibia,  235 

Malabar    squirrel,     biceps    brachii 

in,  78,  79 
Man,  ability  to  raise  arm  in,  50,  51 
development  of  deltoid  in,  51 
erect  posture  of,  basic  factor  in 
maintenance  of,  159,  160 
characteristics  of,  49,  50 
principal  muscular  changes  in 
connection  with,  131 
latest  muscular  functions  to  be 

acquired  by,  50 
shoulder  region,  in,  muscles,  52 
Marsupial  or  epi-pubic  bone,  230, 

242,  243,  244 
Marsupials,    ability    to   raise    fore- 
limb  in,  51 
biceps  brachii  in,  78,  79 
biceps  cruris,  in,  152 
deltoid  function  in,  17 
flexion  of  elbow  and  supination 
of   forearm   differentiated    be- 
tween in,  79 
muscular  system  of,  3,  35 
patency    of    internal    abdominal 

ring  in,  243,  244 
pyramidalis  in,  230 
semi-tendinosus   and   semi-mem- 
branosus  in,  151 
Median  nerve,  division  of,  29 

muscles  supplied  by,  movements, 

85,  86 
paralysis,  84-96 

cases  of,  re-education  in,  93 
movements  *of     thumb     and 

fingers  in,  125 
position  of  anatomical  rest  in, 

9i 

Median  and  musculo-spiral  nerve, 
paralysis,  position  of  ana- 
tomical rest  in,  93 

Median  and  ulnar  nerve,  paralysis, 
position  of  anatomical  rest  in, 
62 

Median  and  ulnar  nerves,  complete 
division,  followed  by  repair  of 
ulnar,  with  portions  of  internal 
cutaneous,  median,  and  great 
sciatic,  106,  107 


26o 


INDEX 


Metacarpo- phalangeal  joints,  action 
of    extensor    communis    digi- 
torum  at,  116 
flexion  at,  116 

flexure  from  over- extension,  ioo 
hyper- extension  at,  116 
two    inner,    hyper-extension    at, 
in  ulnar  paralysis,  104 
Metacarpus,      separate     extending 

muscle  possessed  by,  113 
Metal   splint,    adjustable,    for   rest 
of   fingers   in   re-education    of 
interossei,  108 
("dropped  wrist"),  118 
Monotremes,  biceps  cruris  in,  152 

pyramidalis  in,  230 
Motion,  source  of,  19 
Multifidus  spinae,  action,  208,  217 
divisions  of,  208 
origin  and  insertion,  215 
Muscle,  chronic  shortening,  22 
contraction,  22,  27 
cause,  24,  25 
treatment,  24 
nature  of,  1 
origin,  2,  5 
Muscles,   origin,   adaptation  to  al- 
terations of  distance,  43 
"  survival  value,"  34 
Muscular  action,  evolution  of,  14,  16 

testing  for,  28 
Muscular  power,  1 
Muscularity,  definition  of,  3 
Musculo- cutaneous  nerve,  origin,  71 
paralysis,  positions  of  rest  in, 
how  effected,  80 
Musculo- spiral  nerve,  muscles  sup- 
plied by,  in 
origin  of,  1 1 1 
paralysis,  in 

See  also  Paralysis,  musculo-spiral 
Musculo- spiral  and   median  nerve, 
paralysis,     position     of     ana- 
tomical rest  in,  93 
Musculo-spiral     and     ulnar     nerve 
paralysis,     position     of     ana- 
tomical rest  in,  92 
Myositis,  syphilitic,  28 

Neck,  muscles  moving,  206 

dorsal,  post- vertebral,  or  ex- 
tending, 206 
fixed  point  of  attachment  for, 

213 
ventral,      pre-vertebral,      or 
flexing,  209 
muscles    of,    weakness,    rare    in 
infantile  paralysis,  219 
Nerve  cells,  "  irreparable  damage  " 
to,  15 


Nerve-supply,  double,  of  index  and 

middle  fingers,  107 
Nerves,  contraction  regulated  by,  1 
repair  after  division  of,  29 
will  power  conveyed  by,  19 
See  also  Median  nerve  ;   Musculo- 
spiral  nerve  ;    Peroneal  nerve  ; 
Ulnar    nerve ;     Sciatic    nerve, 
great 
Nervous     mechanism,     constituent 
parts  of,  19 


Obturator     externus,     origin     and 
insertion,  142,  143 
internus,    insertion    in    common 
with     superior     and     inferior 
gemellus,  142 

Occiput,  articulation  of  atlas  with, 
201 
direct   connection   of  axis  with, 

201 
and  atlas,   articulation  between, 
flexion  and  extension  at,   ex- 
ample of  first  order  of  leverage, 
205 

Odontoid  process,  201 

Olecranon,  comparison  with  patella, 

156 
Opponens  pollicis,  action,  87,  91 
Orthograde  posture,  17 
Os  calcis,  function,  171 

in  African  and  European  races 
compared,  171 
Osmosis,  47 
Oxidation  in  relaxation  of  muscle, 

47 


Paralysis,  grafting  in,  18 

infantile,   cause   of   "  paralysis  " 
of  leg  and  foot  muscles,  193 

early,  rest  in  bed  in,  60 

in    relation    to     paralysis     of 
quadriceps,  160,  161 

inutility    of    upper    limb    in, 
cause,  91 

re-education  of  upper  extrem- 
ity in,  65 

results    of    neglected     or    in- 
sufficient rest  in,  220,  221 

weakness  of  neck  muscles  rare 
in,  219 

See  also  Poliomyelitis 
ischaemic,  28 
musculo-cutaneous,  112 

ideal  recovery  aimed  at,  80 

positions  of  rest  in,  80 

re-education    of     muscles     in, 
method,  80 


INDEX 


261 


Paralysis,  musculo- spiral,  in 
anatomical  rest  in,  117 

best  positions  for,  118 
appearances,  113 
contracture  of  flexors  in,   118, 

120,  124 
extension   of   wrist   and   hand 

in,  120 
movements     of     thumb     and 

fingers  in,  124,  125 
recovery    from,     chief    factor 
preventing,  118 
maximum,  test  for,  120 
re-education    of    muscles     in, 
daily  time  required  for,  122 
method,  119 
of  deltoid,  23 

point  of  support,  21 
test  for,  30 
of  flexors  of  ankle,  23 
of  median  nerve,  84-96 

cases  of  re-education  in,  93 
movements     of     thumbs     and 

fingers  in,  124 
position  of  anatomicalrestin,  91 
of    median    and    musculo-spiral 
nerve,  position  of  anatomical 
rest  in,  93 
of  pronators  of  forearm,  23 
of  quadriceps,  23,  160 

test  for,  30 
of  serratus,  58 
of  ulnar  nerve,  97 

anatomical  rest  in,  101 
hyper-extension  of   two  inner 
metacarpo- phalangeal  j  oints 
in,  104 
movements     of     thumb     and 

fingers  in,  124,  125 
partial,  condition  of  fingers  in, 
109 
symptoms  of,  105 
position  of  rest  in,  102,  103 
recovery  of  interossei  in,  106 
re-education     of     muscles    in, 

methods,  103 
weakness  of  interossei  in,  104 
and  median  nerve,  position  of, 

anatomical  rest  in,  92 
and  musculo-spiral  nerve,  posi- 
tion of  anatomical  rest  in,  92 
phrenic,  rarity,  248,  249 
referable  to  loss  of  function,  15 
Paraplegia,     spastic,     of     children, 
contraction  of  gracilis  in,  148 
Paresis  of  muscles  elevating  limb, 

cause  of  stiff  shoulder,  68 
Patella,  fracture  of,  production  by 
quadriceps,  159 
special  function  of,  155,  156,  157 


Pectineus,  origin  and  insertion,  139 
Pectoral  contraction,  67,  68 
Pectoralis  major,   chronic  shorten- 
ing of,  23 
origin  and  insertion,  54 
Pectoralis  minor,  action,  56 

origin  and  insertion,  57 
Pelvic  tilting,  how  produced,  219, 

220,  221 
Peritonitis,     acute,     movement    of 
thoracic    at    expense    of    ab- 
dominal muscles  in,  240 
Peroneal   nerve,    injury   of,    move- 
ments lost  through,  193 
shell    wound    of    upper    leg    in- 
volving, incapacity  resulting 
from,  193 
method   of  rest   treatment   of 
foot  for,  193,  194 
trauma    or    gunshot    injury    of, 
cause   of    "  paralysis  "    of   leg 
and  foot  muscles,  193 
Peroneus  brevis,  comparative  ana- 
tomy of,  181 
direction     of     expansion      from 

tendon,  170 
functions,  173,  177,  179,  180 
origin  and  insertion,  170 
Peroneus    brevis    and    longus,     in 

man,  compared,  181 
Peroneus      longus,      almost      non- 
existent in  kangaroo,  181 
functions,  173,  177,  178,  180 
origin  and  insertion,  173 
position,  173 
tendon  of,  course,  173 
Peroneus  tertius,  functions  of,  173, 
178,  180 
muscle  in  wombat  representing, 

170 
origin  and  insertion,  169 
Phalanges,  middle  and  distal,  lum- 
bricales  not  extensors  of,  90 
of  toes,  middle  and  distal,  motor 

power  for  extension  of,  189 
proximal    and    distal,    extension 
and  flexion,  100 
Phalanx,    distal,    effect   of   flexion 
of     first     or    proximal    inter- 
phalangeal  joint  on,  *ioo 
Plantaris,  171,  172 
function,  173,  174 
tendon  of,  172 
Plants,  power  of  motion  in,  26 
Plaster  of  Paris,   uselessness  of  in 

rest  of  joints,  224,  226 
Platypus,  abdominal  muscles  in,  230 
action  of  quadriceps  in,  16 
gluteus     maximus     and     biceps 
cruris  of,  134,  135 


262 


INDEX 


Platypus,  gracilis  of,  141,  151 
male,  inguinal  region  in,  242 
muscles    on    ventral    surface    of 

thigh  in,  153 
quadriceps  in,  161 
thymus  gland  in,  35 
Poliomyelitis    affecting    abdominal 
muscles,  rest  treatment,  239 
causing   paralysis   of   quadriceps 

extensor,  160 
deformities  of  foot  following,  176 
"  paralysis  "     of    back    muscles 

due  to,  220 
pelvic  tilting  resulting  from,  220, 

221 
thymus  gland  in,  36 
See  also  Paralysis,  infantile. 
Popliteal  nerve,  injury  of,  paralysis 
resulting  from,  rest  treatment 
of  foot  in,  195 
Popliteus,  action,  149 
direct  pull  of,  150 
origin  and  insertion,  149 
production  of  inward  rotation  at 
knee  by,  151 
Poupart's  ligament,  228,  229 

function,  229 
Pressure,      continuously      applied, 

results  of,  26 
Processus  vaginalis,  non- occlusion, 
resulting  in  inguinal  hernia,  242 
Profundus   tendon,    double   supply 

to  middle  finger,  108 
Pronation,  recovery  of,  in  median 
paralysis,  re-education  for,  93 
Pronator  quadratus,  86,  87 

action,  77 
Pronator  teres,  86,  87 
centre  of  motion  for,  77 
contracted  lengthening,  in  cases 
of  old  paralysed  biceps,  83,  84 
course,  76 
Pronators  of  forearm,  paralysis  of, 

23 
Psoas  irritation,  testing  for,  133 
Psoas  major,   of  man,   contraction 
of,  diagnostic  significance,  132 
origin  and  insertion,  130 
selection  and  enlargement  in  man, 

131 
Psoas  minor,  action,  218 

diminution   or   disappearance  in 

man,  131 
great     size     in     kangaroo     and 
platypus,  131 
Pulleys,  examples  of,  8 
Pyramidalis,    in    monotremes    and 
marsupials,  230 
origin,  230 
Pyriformis,  origin  and  insertion,  142 


Quadratus  femoris,  143 
Quadratus  lumborum,  217,  218 
action,  218 
contraction,  218 

origin,  attachment,  and  insertion, 
218 
Quadriceps  extensor,  action  of,  14, 
16 
fulcrum  for  action  of,  158 
functions  of,  50,  157,  158 

evolutionary  aspect,  160,  161 
in   man   and   other    mammals 
compared,  161 
increases  in  man,  functional  not 

structural,  131 
insertion,  155,  156 
muscles  composing,  154 
paralysed,    anatomical     rest    of, 
method  of  application,  162 
application  of  abduction  splint 

in,  162 
misuse  of  term,  160 
recovery  of,  165,  166 
re-education,  commencing,  163, 
164,  165 
knee    movements    in,     165, 

166,  167 
method,  163 

graduated,  163-7 
paralysis,  23,  160 

conditions  wrongly  assumed  to 

be,  160 
due  to  poliomyelitis,  160 
function  of,  loss  and  recovery, 

160,  161 
infantile  paralysis  in  relation 

to,  160,  161 
test  for,  30 

what  constitutes,  160,  161 
production  of  fracture  of  patella 
by,  159 
Quadriceps  extensores,   great  rela- 
tive size  of,  reason  for,  159 

Radius,      muscles     inserted     into, 

action,  77 
Rectus  abdominis,  230,  231 

abnormality  in,  240 

insertion,  231 

situation,  231 
Rectus  capitis  anticus  major,  origin 

and  insertion,  204 
Rectus  capitis  anticus  minor,  course 

of,  204 
Rectus  femoris,  heads  of  origin,  154 

insertion,  154 
Rectus  lateralis,  action,  205 

origin  and  insertion,  204,  205 
Rectus  posticus  major,  203 
Rectus  posticus  minor,  action,  203 


INDEX 


263 


Re-education,  commencing  in  weak- 
ness of  extensors  of  fingers,  107, 
108 
for  muscular  weakness  in  shoul- 
der region,  method  of,  60-67 
for  radial  or  ulnar  deviation  of 

hand,  114 
graduated,  29 

in  cases  of  median  paralysis,  93 
of  muscle  function,  20,  22 
of   muscles   acting   on   foot    and 
toes  in  sciatic  nerve  paralysis, 
192,  194,  195 
of  muscles  in  musculo-cutaneous 
paralysis,  method,  80 
in  ulnar  paralysis,  103 
of  finger  after  suture  of  ulnar 
nerve    after    complete    divi- 
sion, no 
of  paralysed  quadriceps  extensor, 
163,  164-167 
Reflex  movements,  161 
Relaxation,  physiological  action  of, 

36 
stimulus  to,  40 
Renuentes,  203 
Reptiles,    abdominal    situation    of 

lungs  in,  235 
Respiration,     abdominal,     diminu- 
tion of,  grave  import  of,  240 
muscles  of,  228-49 
principal  muscle  of,  234 
Respiratory  mechanism,  voluntary 
and     involuntary     action     of 
muscles  in,  234 
Respiratory  movements,  essence  of, 

234 
of  abdominal  viscera,  236 
Rest,  anatomical,  in  musculo- spiral 
paralysis,  117 
and     re-education,     of     muscles 
acting  on  foot  and  toes  in 
sciatic  nerve  paralysis,  192, 

194.  195 
recovery  from   "  paralysis  " 
of   right   foot   due   to  in- 
fantile    paralysis,      after, 

195-  196 
result  in  case  of  shell  wound 
injury     of     great     sciatic 
nerve,  196 
in  treatment,  19,  21 
of  joints,  positions  for,  222-7 
of  muscles,  what  constitutes,  20 

zero  position,  18 
physiological,  18 

treatment  of  poliomyelitis  affect- 
ing abdominal  muscles,  239 
zero  position  of,  18,  21 
Reverse  action,  muscular,  41 


Rhomboids,  action,  56 
antagonist,  56 
origin  and  insertion,  57 
Ribs,  action,  centre  of  motion  for, 
213,  247 
function,  246,  247 
true  muscles  of,  232 
See  also  Cervical  ribs 
Riding,  muscles  used  in,  139 
Riolan,    function   of   serratus   pos- 
ticus inferior,  248 
Rotatores,  action,  217 

spinie,  215 
Running,  muscles  employed  in,  174, 

180 
Russell,    Hamilton,    cause    of    in- 
guinal hernia  in  children,  241 

Sacro-iliac  joint,  disease  of,  psoas 

contraction  diagnostic  of,  132 
Sarcolemma,  1 

Sartorius,    fulcrum    or    centre    for 
action  of,  147 
function  in  kangaroo,  152 
origin,    insertion,    and   functions 

146,  147,  148,  151 
reverse  action  of,  42 
Scaleni,  209 

action,  211,  212 
course,  211 
Scalenus  anticus,  211 
medius,  211 
posticus,  211 
Scapula,  elevation  of,  in  paralysis 
of  serratus,  58 
muscles  acting  on,  56 
paralysed,  re-education,  64 
rotation,  57,  58 

arc   of   movement  in,   61,    62, 
64,  65 
winging  of,  58,  60 
Sciatic     nerve,     great,     in     thigh, 
injury    of,    mischief    resulting 
from,  193 
paralysis    following,     treatment, 

195 

rest  and  re-education  of  muscles 

acting  on  foot  and  toes  in,  192, 

194.  J95 
severance  by  shell  wound,  result 
of  treatment  by  rest  and  re- 
education of  muscles,  196 
trauma    or    gunshot    injury    of, 
cause  of  paralysis  of  leg  and 
foot  muscles,  193 
Semi-membranosus,  origin  and  in- 
sertion, 148 
Semi-spinales,  207 
action,  217 

on  one  or  both  sides,  208 


264 


INDEX 


Semi-spinales,  not  found  in  lumbar 
region,  217 
origin  and  insertion,  208 
Semi-spinalis,  course,  215 
Semi-tendinosus,  origin  and  inser- 
tion, 148 
and  semi-membranosus  in  mar- 
supials, 151 
Serratus,  loss  of  muscular  power  in, 
position  of  anatomical  rest  for, 
59,  60 
paralysis  of,  58 
Serratus  magnus,  or  anterior,  action, 
56 
origin  and  insertion,  56,  57 
Serratus  posticus  inferior,  233 

function,  248 
Serratus  posticus  superior,  233 

function,  247 
Sesamoid  bones,  8 

development,  184,  185 
Shell  wound  causing  severance  of 
great   sciatic   nerve,    result   of 
treatment    by    rest    and    re- 
education of  muscles,  196 
of  upper  leg  involving  peroneal 
nerve,      incapacity      resulting 
from,  193 
Shoulder- joint,     diseases     and    in- 
juries,    involvement    of    long 
head  of  biceps  in,  79 
excision  of,  division  of  long  head 

of  biceps  avoided  during,  75 
loss  of  muscular  power  in,  benefit 
of  rest  in  bed  during,  60 
Shoulder  region,  in  man,  muscles  of, 
52 
loss  of  muscular  power  in,  posi- 
tions of  anatomical  rest  for,  58 
muscular  weakness  in,  re-educa- 
tion for,  method,  60-7 
Sitting,  action  of  knee  flexors  in,  150 
flexion  and  extension  of  leg  on 

thigh  during,  150 
flexion  at  hip-joint  during,  150 
Skeletal  balance  apart  from  muscu- 
lar action,  non-existent,  219 
muscles,  number  and  weight  of,  1 
Soleus,  function  of,  173,  174 
knee  joint  not  crossed  by,  171 
origin  and  insertion,  171 
Spastic    diseases    of    children,    im- 
pediment to  walking  in,  140 
Spinal  cord,   relation  to   muscular 

action,  161 
Spinalis  dorsi,  origin  and  insertion, 

215 
Spine,  area  of  greatest  mobility  of, 
206 
centre  of  motion  of  ribs  at,  213 


Spine,   cervical,   lateral  movement, 
how  effected,  212 
effects  of  flexion  and  extension 

of  hip,  on,  132 
elasticity,  213,  214 
fixed  point  for  action  of  inter- 
costal muscles,  213 
flexion  movement  in,  area  where 

greatest,  213 
front  of,  muscles  on,  for  flexion 

few,  for  extension  many,  218 
lateral     curvature     of,     due     to 
insufficient    rest    in    infantile 
paralysis,  220 
movements  of  head  on,  201 
muscles  of,  200-5 

post-vertebral     or     extending, 

201,  202 
pre- vertebral,  or  bending,  204 
weakness  ("  paralysis  ")  due  to 
poliomyelitis,  220 
treatment  by  rest  of  trunk 
and  lower  limb  in  double 
Thomas's  splint,  220 
thoracic,  fixed  point  for  attach- 
ment   of    muscles    acting    on 
neck,  213 
thoracic  region,  flexion  and  ex- 
tension practically  absent  in, 
213,  217 
no  pre- vertebral  muscle  in,  217 
Splenius  capitis,  202 
action,  202 

origin  and  insertion,  202 
Splenius  cervicis,  206,  207 

action  of  one  or  both  muscles,  207 
origin  and  insertion,  207 
Splenius  colli,  202 
Splint,     "  cock- up,"     for     rest     of 
hand   in   paralysis   of   wrist 
extenders,  118,  119 
See    also    Aluminium    "  cock- 
up  "  splint 
dorsal  hip  (Thomas's),  133 
for  abduction  of  upper  limb,  in 

ulnar  paralysis,  103 
Lister's,    for  rest  of   wrist- joint, 

226 
method  of  application  in  rest  of 
foot,     in     gunshot    injury    of 
peroneal  nerve,  193 
Thomas's,    double,    for    rest    of 
trunk    and    lower    limbs    in 
"  paralysis  "  of  back  muscles 
220 
single,  with  arc  shoe  attached, 
for  rest  of  knee  joint,  225 
Standing  erect,  muscles  used  in,  139 
on  tiptoe,  muscles  employed  in, 
174,  180 


INDEX 


265 


Sternoclavicular  articulation,  con- 
nection of  upper  extremity  with 
trunk  at,  57 

Sterno- mastoid,   fulcrum  or  centre 
of  motion  of,  205 
origin  and  insertion,  205 

Sterno-mastoids,  action  of  one  or 
both  contrasted,  205 

Stiff  shoulder,  67,  68 
causal  factors,  68 
treatment,  69,  70 

Structural  correlations,  30 

Sublimis,  contraction  in  ulnar 
paralysis,  how  resulting,  no 

Subscapularis,  origin  and  insertion, 

55 
Superior  oblique,  action,  204 

origin  and  insertion,  203 
Supinator  brevis,  centre  of  motion 
for,  77 
course,  76 
insertion,  113 

order  and  position  of  origin,  in 
power,  112 

re-education     in     musculo-spiral 
paralysis,  122 
Supinator  longus,  34 
Supinators,    stimulus    to    contrac 

tion  of,  41 
Supracostales.     See  Levatores  cos- 

tarum 
Supraspinatus,  action,  51 
function,  57 
origin  and  insertion,  54 
"  Survival  value  "  of  muscles,  34 
Synergists,  examples  of,  45 
Syphilitic  myositis,  28 

Talipes     calcaneus,     deformity     of 
foot  present  in,  176,  179 
rest  treatment,  192 
result  of  poliomyelitis  in  child- 
hood, 176 
Talipes  equinus,  deformity  of  foot 
present  in,  176,  179 
result  of  poliomyelitis  in  child- 
hood, 176 
treatment,  24 
by  rest,  192 
Talipes  valgus,  179 

treatment,  181 
Talipes  varus,  179 

in  children,  treatment,  183 
Tasmanian  devil,  cremaster  muscle 
in,  244 
muscular  system  of,  3 
Tendinous  insertion,  2 
Tendo  achillis,   chronic  shortening 
of,  23 
contracted  chronically,  24 


Tendo    achillis,    contraction,    pre- 
vention, 27 
formation,  171 

muscles    acting    through,    func- 
tions, 174 
superficial  portion,  171 
and  tibialis  posticus,  contraction 
of,  treatment,  194 
Tendon,  force  and  leverage  due  to,  3 
insertion  into  bone,  3 
of     extensor     communis     digiti, 
how  elongated,  117 
position  and  shape,  116 
of  origin  of  muscle,  2 
of  peroneus  longus,  course,  173 
fibro-cartilage  formed  in,  173 
of  plantaris,  172 
of  tibialis  posticus.  172,  173 
shortening  of,  24 
tissue,  limitations  of,  3 
transplantation,   in  thumb  drop 
with  paralysis  of  muscles,  113 
Tendons,  elongation  of,  27 
long,  of  interossei,  10 1 
of  extensor  communis  digitorum, 

114 
of  foot,  treatment  of,  inequinus,  24 
of  gastrocnemius,  170 
of    interossei,    connections    with 
communis  tendons,  116 
how  elongated,  117 
Tensor  fasciae   femoris,    origin,   in- 
sertion, and  work  of,  141,  142 
Teres  major,  function,  55 
origin  and  insertion,  55 
tendon,  55 
Teres  minor,  origin  and  insertion,  54 
Test  for  action  of  flexors,  29 
for  deltoid  paralysis,  30 
for  muscle  action,  28 
for  paralysis  of  brachialis,  9 
for  paralysis  of  quadriceps,  30 
volitional,  16,  28 
Testes,  descent  of,  241 
Thigh,  abduction  of,  141 
action  of  adductors  on,  139 
external    and    internal    rotation, 

muscles  effecting,  142 
flexion,    pathological    conditions 

associated  with,  132 
flexion  and  extension  of  leg  on, 
during  sitting,  150 
of  trunk  of  body  on,  129 
muscles  of,  127-142 

regions  of  insertion,  128 
on  ventral  surface  of,  in  platy- 
pus, 153 
and  trunk,   rigid,   bending  back 
at  knee  joints  by  acrobat  and 
athletes,  156 


266 


INDEX 


Thomas,  H.  O.,  angle  of  flexion  for 
rest  of  elbow  joint,  227 
method  of  resting  hip  joint,  132, 

133 
treatment   of   "  dropped   wrist," 
119 
Thomas's       splints.     See       Caliper 
splint,    Dropped    wrist    metal 
splint,     Hand     splint,     Splint, 
Thomas's 
Thorax,  muscles  of,  232 
function,  246 

movement  at  expense  of  ab- 
dominal, in  inflammatory  con- 
ditions of  abdomen,  240 
Thumb,  abduction  of,  important 
factor  in,  126 
drop  with  paralysis  of  muscles, 
tendon      transplantation      in, 

113 
extension,       in       musculo-spiral 

paralysis,  117 
flexion,  in  ulnar  paralysis,    102, 

104 
long  abductor  of,  rest  in  musculo- 
spiral  paralysis,  117 
motor  forces  moving,  86 
movement      in      human      hand, 

specialization,  how  manifested, 

113 
movements    in    median,     ulnar, 

and    musculo-spiral    paralysis, 

124-6 
muscles  of,  loss  of  function  in, 
223 

re-education  in  ulnar  paralysis, 
104 
opposition,  87 

and    flexion,    recovery    of    in 
median  nerve  paralysis,  re- 
education for,  95 
small  muscles  of,  98 
Thymus  gland  and  development  of 

muscle,  34 
use  of,  in  poliomyelitis,  36 
Tibia  compared  with  fibula,  17 
relation  of  olecranon  to,  156 
Tibialis  anticus,  division  in  talipes 

varus,  183 
functions,  173,  177,  178,  180 
in  saltatorial  kangaroo,  178 
origin  and  insertion,  168 
Tibialis  posticus,   absence  in  kan- 
garoo, 178 
functions,  173,  177,  178,  194 
origin,  172 
tendon  of,  172 

insertion,  173 
and  tendo  achillis,  contraction  of, 

treatment,  194 


Toe,  big,  bunion  of,  186 

flexors  of,  action  improved  by 

leverage,  185 
two  separate  extending  muscles 

of,  183 
See  also  Hallux 
little,  adducting  power  of,  186 
production  of  extension  in,  189 
Toes,  abductors  and  adductors  of, 
191 
even  extension,  189 
flexors  of,  action,  190 
four    lesser,    abductors    and    ad- 
ductors of,  191 
extensors  of,  188 
flexors  of,  189 
muscles  acting  on,  188 
lateral  action,  imaginary  line  for, 

191 
muscles  of,  182 
Trachelo- mastoid,  action,  203 

origin  and  insertion,  203 
Tracheotomy  in  epigastric  retrac- 
tion, 249 
Transversalis,  aponeurosis  of,  229 
abdominis,  action,  248 
cervicis,  206,  207 
action,  207 

origin  and  insertion,  207 
origin,  229 

sheet,    primitive,    muscular    sys- 
tem developed  from,  238 
Transversus  pedis,  186 
Trapezius,  action,  56,  58 
function,  56 

loss  of  muscular  power  in,  treat- 
ment by  abduction  of  arm,  '58 
origin  and  insertion,  56 
Trapezoid,  57 
Triangular  fascia,  230 
Triceps,  in,  112 

anatomical  rest  of,  in  musculo- 
spiral  paralysis,  117 
antagonist  of,  112 
origin  of,  ill,  117 
power  of,  112 
re-education     in     musculo-spiral 

.paralysis,  123 
relaxation    does    not    permit    of 

supination,  78 
stimulus  to  contraction  of,  41 
Trunk  of  body,flexion  and  extension 
on  thigh,  129 
and  thigh,  rigid,  bending  back  at 
knee  joints    by  acrobats    and 
athletes,  150 

Ulnar   nerve,    branches    arising   in 
forearm,  97 
division  of,  29 


INDEX 


267 


Ulnar  nerve,  origin,  97 
paralysis,  97 

anatomical  rest  in,  101 
movements     of     thumb     and. 

fingers  in,  124,  125 
position  of  rest  in,  102,  103 
re-education     of     muscles     in, 
methods,  103 
suture  for  complete  division,  fol- 
lowed by  early  re-education  of 
muscles,  no 
Ulnar  and  median  nerve  paralysis, 
position  of  anatomical  rest  in, 
92 
Ulnar  and  median  nerves,  complete 
division,  followed  by  repair  of 
ulnar,  with  portions  of  internal 
cutaneous,   median,   and  great 
sciatic,  106 
Ulnar    and    musculo-spiral    nerve, 
position  of  anatomical  rest  in, 
92 
Upper  limb  abduction  splint,  227 
in  ulnar  paralysis,  103 

Vastus,  externus  or  lateralis,  origin 
and  insertion,  154 
internus  or  medialis,  connection  ( 
with  crureus,  154,  155 
extension  of,  155 
origin,  154 
Vertebrje,    individual    motion    be- 
tween, limited,  213 
lumbar,    disease    of,    psoas    con- 
traction as  diagnostic  of,  132 
Viscera,  support  of,  by  abdominal 

muscles,  239 
Visceroptosis,  cause  of,  240 

cause    of    greater    frequency    in 
women,  240,  241 
Volition,  normal  muscle  contracted 

by,  25 
Volitional  test,  16 
for  muscle  action.  28 


Walking,  impediment  to   in  spastic 
diseases  of  children,  140 
muscles  employed  in,  174,  180 
Will  power,  conveyed  by  nerves,  19 
Wombat,  biceps  brachii  in,  78,  79 
brachio-radialis  in,  73 
cremaster  muscle  in,  244 
dissection  of  inner  side  of  knee 

in,  152 
male,  inguinal  region  in,  245 
patent  internal  abdominal  ring 
and  canal  in,  243 
muscle      representing      peroneus 

tertius  in,  170 
muscular  system  of,  3,  35 
peroneus  longus  in,  181 
Women,  cause  of  greater  frequency 
of  visceroptosis  in,  240,  241 
frequency  of  hallux  valgus  in,  187 
Wrist-joint,     diseased    or    injured, 
splints  for  use  in  rest  of,  226 
extension,  position  of,  effect  on 
flexion    of   fingers   in    ulnar 
paralysis,  109 
promoting      improvement      of 
flexor  leverage  of  fingers,  96 
extensors,  abduction  power,  113, 
114 
abduction  power,  in  connection 
with  re-education  for  radial 
or  ulnar  deviation  of  hand,  114 
order   and   position   of   origin, 

in,  112 
paralysis  of,  splint  for  rest  of 
hand  in,  118 
flexion,  in  ulnar  paralysis,  10 1 
recovery  of  in  median  paralysis, 
re-education  for,  94 
flexors  of,  testing  of,  29 
forces  acting  on,  40 
and  hand,  extension,  in  musculo- 
spiral  paralysis,  120 

Zero  position  of  rest,  18,  21 


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